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1.  Whole-Genome Sequencing of a Single Proband Together with Linkage Analysis Identifies a Mendelian Disease Gene 
PLoS Genetics  2010;6(6):e1000991.
Although more than 2,400 genes have been shown to contain variants that cause Mendelian disease, there are still several thousand such diseases yet to be molecularly defined. The ability of new whole-genome sequencing technologies to rapidly indentify most of the genetic variants in any given genome opens an exciting opportunity to identify these disease genes. Here we sequenced the whole genome of a single patient with the dominant Mendelian disease, metachondromatosis (OMIM 156250), and used partial linkage data from her small family to focus our search for the responsible variant. In the proband, we identified an 11 bp deletion in exon four of PTPN11, which alters frame, results in premature translation termination, and co-segregates with the phenotype. In a second metachondromatosis family, we confirmed our result by identifying a nonsense mutation in exon 4 of PTPN11 that also co-segregates with the phenotype. Sequencing PTPN11 exon 4 in 469 controls showed no such protein truncating variants, supporting the pathogenicity of these two mutations. This combination of a new technology and a classical genetic approach provides a powerful strategy to discover the genes responsible for unexplained Mendelian disorders.
Author Summary
Metachondromatosis (MC) is an autosomal dominant condition characterized by exostoses (osteochondromas), commonly of the hands and feet, and enchondromas of long bone metaphyses and iliac crests. MC exostoses may regress or even resolve over time, and short stature is not characteristic of MC. Here, we sequenced the whole genome of a single patient with MC and used partial linkage data from her small family to focus our search for the responsible variant. In the proband, we identified an 11 bp deletion in exon four of PTPN11, which results in premature translation termination and co-segregates with the phenotype. In a second metachondromatosis family, we identified a nonsense mutation in exon 4 of PTPN11 that also co-segregates with the phenotype. Germline gain-of-function missense mutations in PTPN11 cause an overlapping but distinct group of dominant disorders with involvement of the face, heart, skeleton, skin, and brain, including Noonan syndrome (OMIM 163950), Noonan-like disorder with multiple giant cell lesion syndrome (OMIM 163955), and LEOPARD syndrome (OMIM 151100). Nonsense mutations in PTPN11 have not been described in humans and the loss-of-function PTPN11 mutations we report here are the first to be described in human disease.
doi:10.1371/journal.pgen.1000991
PMCID: PMC2887469  PMID: 20577567
2.  Osteopoikilosis and multiple exostoses caused by novel mutations in LEMD3 and EXT1 genes respectively - coincidence within one family 
BMC Medical Genetics  2010;11:110.
Background
Osteopoikilosis is a rare autosomal dominant genetic disorder, characterised by the occurrence of the hyperostotic spots preferentially localized in the epiphyses and metaphyses of the long bones, and in the carpal and tarsal bones [1]. Heterozygous LEMD3 gene mutations were shown to be the primary cause of the disease [2]. Association of the primarily asymptomatic osteopokilosis with connective tissue nevi of the skin is categorized as Buschke-Ollendorff syndrome (BOS) [3]. Additionally, osteopoikilosis can coincide with melorheostosis (MRO), a more severe bone disease characterised by the ectopic bone formation on the periosteal and endosteal surface of the long bones [4-6]. However, not all MRO affected individuals carry germ-line LEMD3 mutations [7]. Thus, the genetic cause of MRO remains unknown. Here we describe a familial case of osteopoikilosis in which a novel heterozygous LEMD3 mutation coincides with a novel mutation in EXT1, a gene involved in aetiology of multiple exostosis syndrome. The patients affected with both LEMD3 and EXT1 gene mutations displayed typical features of the osteopoikilosis. There were no additional skeletal manifestations detected however, various non-skeletal pathologies coincided in this group.
Methods
We investigated LEMD3 and EXT1 in the three-generation family from Poland, with 5 patients affected with osteopoikilosis and one child affected with multiple exostoses.
Results
We found a novel c.2203C > T (p.R735X) mutation in exon 9 of LEMD3, resulting in a premature stop codon at amino acid position 735. The mutation co-segregates with the osteopoikilosis phenotype and was not found in 200 ethnically matched controls. Another new substitution G > A was found in EXT1 gene at position 1732 (cDNA) in Exon 9 (p.A578T) in three out of five osteopoikilosis affected family members. Evolutionary conservation of the affected amino acid suggested possible functional relevance, however no additional skeletal manifestations were observed other then those specific for osteopoikilosis. Finally in one member of the family we found a splice site mutation in the EXT1 gene intron 5 (IVS5-2 A > G) resulting in the deletion of 9 bp of cDNA encoding three evolutionarily conserved amino acid residues. This child patient suffered from a severe form of exostoses, thus a causal relationship can be postulated.
Conclusions
We identified a new mutation in LEMD3 gene, accounting for the familial case of osteopoikilosis. In the same family we identified two novel EXT1 gene mutations. One of them A598T co-incided with the LEMD3 mutation. Co-incidence of LEMD3 and EXT1 gene mutations was not associated with a more severe skeletal phenotype in those patients.
doi:10.1186/1471-2350-11-110
PMCID: PMC2912259  PMID: 20618940
3.  Mutational screening of EXT1 and EXT2 genes in Polish patients with hereditary multiple exostoses 
Journal of Applied Genetics  2014;55:183-188.
Hereditary multiple exostoses (HME) also known as multiple osteochondromas represent one of the most frequent bone tumor disorder in humans. Its clinical presentation is characterized by the presence of multiple benign cartilage-capped tumors located most commonly in the juxta-epiphyseal portions of long bones. HME are usually inherited in autosomal dominant manner, however de novo mutations can also occur. In most patients, the disease is caused by alterations in the EXT1 and EXT2 genes. In this study we investigated 33 unrelated Polish probands with the clinical and radiological diagnosis of HME by means of Sanger sequencing and MLPA for all coding exons of EXT1 and EXT2. We demonstrated EXT1 and EXT2 heterozygous mutations in 18 (54.6 %) and ten (30.3 %) probands respectively, which represents a total of 28 (84.9 %) index cases. Sequencing allowed for the detection of causative changes in 26 (78.8 %) probands, whereas MLPA showed intragenic deletions in two (6.1 %) further cases (15 mutations represented novel changes). Our paper is the first report on the results of exhaustive mutational screening of both EXT1/EXT2 genes in Polish patients. The proportion of EXT1/EXT2 mutations in our group was similar to other Caucasian cohorts. However, we found that EXT1 lesions in Polish patients cluster in exons 1 and 2 (55.6 % of all EXT1 mutations). This important finding should lead to the optimization of cost-effectiveness rate of HME diagnostic testing. Therefore, the diagnostic algorithm for HME should include EXT1 sequencing (starting with exons 1–2), followed by EXT2 sequencing, and MLPA/qPCR for intragenic copy number changes.
doi:10.1007/s13353-014-0195-z
PMCID: PMC3990859  PMID: 24532482
EXT1; EXT2; Hereditary multiple exostoses; Multiple osteochondromas; Mutation; Polish patients
4.  Loss-of-Function Mutations in PTPN11 Cause Metachondromatosis, but Not Ollier Disease or Maffucci Syndrome 
PLoS Genetics  2011;7(4):e1002050.
Metachondromatosis (MC) is a rare, autosomal dominant, incompletely penetrant combined exostosis and enchondromatosis tumor syndrome. MC is clinically distinct from other multiple exostosis or multiple enchondromatosis syndromes and is unlinked to EXT1 and EXT2, the genes responsible for autosomal dominant multiple osteochondromas (MO). To identify a gene for MC, we performed linkage analysis with high-density SNP arrays in a single family, used a targeted array to capture exons and promoter sequences from the linked interval in 16 participants from 11 MC families, and sequenced the captured DNA using high-throughput parallel sequencing technologies. DNA capture and parallel sequencing identified heterozygous putative loss-of-function mutations in PTPN11 in 4 of the 11 families. Sanger sequence analysis of PTPN11 coding regions in a total of 17 MC families identified mutations in 10 of them (5 frameshift, 2 nonsense, and 3 splice-site mutations). Copy number analysis of sequencing reads from a second targeted capture that included the entire PTPN11 gene identified an additional family with a 15 kb deletion spanning exon 7 of PTPN11. Microdissected MC lesions from two patients with PTPN11 mutations demonstrated loss-of-heterozygosity for the wild-type allele. We next sequenced PTPN11 in DNA samples from 54 patients with the multiple enchondromatosis disorders Ollier disease or Maffucci syndrome, but found no coding sequence PTPN11 mutations. We conclude that heterozygous loss-of-function mutations in PTPN11 are a frequent cause of MC, that lesions in patients with MC appear to arise following a “second hit,” that MC may be locus heterogeneous since 1 familial and 5 sporadically occurring cases lacked obvious disease-causing PTPN11 mutations, and that PTPN11 mutations are not a common cause of Ollier disease or Maffucci syndrome.
Author Summary
Children with cartilage tumor syndromes form multiple tumors of cartilage next to joints. These tumors can occur inside the bones, as with Ollier disease and Maffuci syndrome, or on the surface of bones, as in the Multiple Osteochondroma syndrome (MO). In a hybrid syndrome, called metachondromatosis (MC), patients develop tumors both on and within bones. Only the genes causing MO are known. Since MC is inherited, we studied genetic markers in an affected family and found a region of the genome, encompassing 100 genes, always passed on to affected members. Using a recently developed method, we captured and sequenced all 100 genes in multiple families and found mutations in one gene, PTPN11, in 11 of 17 families. Patients with MC have one mutant copy of PTPN11 from their affected parent and one normal copy from their unaffected parent in all cells. We found that the normal copy is additionally lost in cartilage cells that form tumors, giving rise to cells without PTPN11. Mutations in PTPN11 were not found in other cartilage tumor syndromes, including Ollier disease and Maffucci syndrome. We are currently working to understand how loss of PTPN11 in cartilage cells causes tumors to form.
doi:10.1371/journal.pgen.1002050
PMCID: PMC3077396  PMID: 21533187
5.  Multiple osteochondromas 
Multiple osteochondromas (MO) is characterised by development of two or more cartilage capped bony outgrowths (osteochondromas) of the long bones. The prevalence is estimated at 1:50,000, and it seems to be higher in males (male-to-female ratio 1.5:1). Osteochondromas develop and increase in size in the first decade of life, ceasing to grow when the growth plates close at puberty. They are pedunculated or sessile (broad base) and can vary widely in size. The number of osteochondromas may vary significantly within and between families, the mean number of locations is 15–18. The majority are asymptomatic and located in bones that develop from cartilage, especially the long bones of the extremities, predominantly around the knee. The facial bones are not affected. Osteochondromas may cause pain, functional problems and deformities, especially of the forearm, that may be reason for surgical removal. The most important complication is malignant transformation of osteochondroma towards secondary peripheral chondrosarcoma, which is estimated to occur in 0.5–5%. MO is an autosomal dominant disorder and is genetically heterogeneous. In almost 90% of MO patients germline mutations in the tumour suppressor genes EXT1 or EXT2 are found. The EXT genes encode glycosyltransferases, catalyzing heparan sulphate polymerization. The diagnosis is based on radiological and clinical documentation, supplemented with, if available, histological evaluation of osteochondromas. If the exact mutation is known antenatal diagnosis is technically possible. MO should be distinguished from metachondromatosis, dysplasia epiphysealis hemimelica and Ollier disease. Osteochondromas are benign lesions and do not affect life expectancy. Management includes removal of osteochondromas when they give complaints. Removed osteochondromas should be examined for malignant transformation towards secondary peripheral chondrosarcoma. Patients should be well instructed and regular follow-up for early detection of malignancy seems justified. For secondary peripheral chondrosarcoma, en-bloc resection of the lesion and its pseudocapsule with tumour-free margins, preferably in a bone tumour referral centre, should be performed.
doi:10.1186/1750-1172-3-3
PMCID: PMC2276198  PMID: 18271966
6.  Targeted Disruption of Shp2 in Chondrocytes Leads to Metachondromatosis With Multiple Cartilaginous Protrusions 
Metachondromatosis is a benign bone disease predominantly observed in the hands and feet of children or young adults demonstrating two different manifestations: a cartilage-capped bony outgrowth on the surface of the bone called exostosis and ectopic cartilaginous nodules inside the bone called enchondroma. Recently, it has been reported that loss-of-function mutations of the SHP2 gene, which encodes the SHP2 protein tyrosine phosphatase, are associated with metachondromatosis. The purpose of this study was to investigate the role of SHP2 in postnatal cartilage development, which is largely unknown. We disrupted Shp2 during the postnatal stage of mouse development in a chondrocyte-specific manner using a tamoxifen-inducible system. We found tumor-like nodules on the hands and feet within a month after the initial induction. The SHP2-deficient mice demonstrated an exostosis-like and enchondroma-like phenotype in multiple bones of the hands, feet, and ribs as assessed by X-ray and micro-computed tomography (CT). Histological assessment revealed the disorganization of the growth plate cartilage, a cartilaginous protrusion from the epiphyseal bone, and ectopic cartilage nodules within the bones, which is consistent with the pathological features of metachondromatosis in humans (ie, both exostosis and enchondroma). At molecular levels, we observed an abundant expression of Indian hedgehog protein (IHH) and fibroblast growth factor 2 (FGF2) and impaired expression of mitogen-activated protein kinases (MAPK) in the affected cartilage nodules in the SHP2-deficient mice. In summary, we have generated a mouse model of metachondromatosis that includes manifestations of exostosis and enchondroma. This study provides a novel model for the investigation of the pathophysiology of the disease and advances the understanding of metachondromatosis. This model will be useful to identify molecular mechanisms for the disease cause and progression as well as to develop new therapeutic strategies in the
doi:10.1002/jbmr.2062
PMCID: PMC4081537  PMID: 23929766
EXOSTOSIS; ENCHONDROMA; CARTILAGE-SPECIFIC KNOCK-OUT MOUSE; SHP2; METACHONDROMATOSIS
7.  COMPOUND HETEROZYGOUS LOSS OF Ext1 AND Ext2 IS SUFFICIENT FOR FORMATION OF MULTIPLE EXOSTOSES IN POSTNATAL MOUSE LONG BONES IN MICE 
Bone  2011;48(5):979-987.
Multiple Hereditary Exostoses (MHE) syndrome is caused by haploinsufficiency in Golgi-associated heparan sulfate polymerases EXT1 or EXT2 and is characterized by formation of exostoses next to growing long bones and other skeletal elements. Recent mouse studies have indicated that formation of stereotypic exostoses requires a complete loss of Ext expression, suggesting that a similar local loss of EXT function may underlie exostosis formation in patients. To further test this possibility and gain greater insights into pathogenic mechanisms, we created heterozygous Ext1+/− and compound Ext1+/−/Ext2+/− mice. Like Ext2+/− mice described previously (Stickens et al. Development 132:5055), Ext1+/− mice displayed rib-associated exostosis-like outgrowths only. However, compound heterozygous mice had nearly twice as many outgrowths and, more importantly, displayed stereotypic growth plate-like exostoses along their long bones. Ext1+/−Ext2+/− exostoses contained very low levels of immuno-detectable heparan sulfate, and Ext1+/−Ext2+/− chondrocytes, endothelial cells and fibroblasts in vitro produced shortened heparan sulfate chains compared to controls and responded less vigorously to exogenous factors such as FGF-18. We also found that rib outgrowths formed in Ext1f/+Col2Cre and Ext1f/+Dermo1Cre mice, suggesting that ectopic skeletal tissue can be induced by conditional Ext ablation in local chondrogenic and/or perichondrial cells. The study indicates that formation of stereotypic exostoses requires a significant, but not complete, loss of Ext expression and that exostosis incidence and phenotype are intimately sensitive to, and inversely related to, Ext expression. The data also indicate that the nature and organization of ectopic tissue may be influenced by site-specific anatomical cues and mechanisms.
doi:10.1016/j.bone.2011.02.001
PMCID: PMC3335264  PMID: 21310272
Multiple Hereditary Exostoses; exostosins; heparan sulfate; mouse mutants; chondrocytes
8.  Acroform type of enchondromatosis associated with severe vertebral involvement and facial dysmorphism in a boy with a new variant of enchondromatosis type I1 of Spranger: case report and a review of the literature 
Cases Journal  2008;1:324.
Background
Enchondromatosis represent a heterogenous group of disorders. Spranger et al attempted a classification into 6 types: Ollier disease, Maffuci syndrome, metachondromatosis, spondyloenchondrodysplasia, enchondromatosis with irregular vertebral lesions, and generalized enchondromatosis. Halal and Azouz added 3 tentative categories to the 6 in the classification of Spranger et al.
Case presentation
We report on a 15-year-old boy with acrofrom upper limbs and mixed appearance of radiolucency, cysts and striae of fibro-chondromatosis. Lower limbs (femoral, tibial and fibular dysplasia showed enlarged metaphyses near the knees bilaterally) were present. Additional features of short stature, macrocephaly, facial dysmorphism, and generalised platyspondyly have been encountered. These bone shortenings were associated with bone bending, curving and rhizomelia of the upper limbs with significant macrodactyly. Limitations in articular movements were present. The forearm deformities were similar to those observed in hereditary multiple exostosis.
Conclusion
The acrofrom upper limbs with mixed appearances of radiolucencies, cysts and striae of fibro-chondromatosis are the basic features of type I1Spranger. The constellation of facial dysmorphic features and significant vertebral abnormalities in our present patient were not compatible with the above-mentioned type of enchondromatosis. Our report widens the knowledge of disorders characterised by enchondromatosis. Ascertainment of the mode of inheritance in our present patient was difficult because of insufficient family history and parents declined clinical/radiographic documentation.
doi:10.1186/1757-1626-1-324
PMCID: PMC2600790  PMID: 19017386
9.  SHP2 Regulates Chondrocyte Terminal Differentiation, Growth Plate Architecture and Skeletal Cell Fates 
PLoS Genetics  2014;10(5):e1004364.
Loss of PTPN11/SHP2 in mice or in human metachondromatosis (MC) patients causes benign cartilage tumors on the bone surface (exostoses) and within bones (enchondromas). To elucidate the mechanisms underlying cartilage tumor formation, we investigated the role of SHP2 in the specification, maturation and organization of chondrocytes. Firstly, we studied chondrocyte maturation by performing RNA-seq on primary chondrocyte pellet cultures. We found that SHP2 depletion, or inhibition of the ERK1/2 pathway, delays the terminal differentiation of chondrocytes from the early-hypertrophic to the late-hypertrophic stage. Secondly, we studied chondrocyte maturation and organization in mice with a mosaic postnatal inactivation of Ptpn11 in chondrocytes. We found that the vertebral growth plates of these mice have expanded domains of early-hypertrophic chondrocytes that have not yet terminally differentiated, and their enchondroma-like lesions arise from chondrocytes displaced from the growth plate due to a disruption in the organization of maturation and ossification zones. Furthermore, we observed that lesions from human MC patients also display disorganized chondrocyte maturation zones. Next, we found that inactivation of Ptpn11 in Fsp1-Cre-expressing fibroblasts induces exostosis-like outgrowths, suggesting that loss of SHP2 in cells on the bone surface and at bone-ligament attachment sites induces ectopic chondrogenesis. Finally, we performed lineage tracing to show that exostoses and enchondromas in mice likely contain mixtures of wild-type and SHP2-deficient chondrocytes. Together, these data indicate that in patients with MC, who are heterozygous for inherited PTPN11 loss-of-function mutations, second-hit mutations in PTPN11 can induce enchondromas by disrupting the organization and delaying the terminal differentiation of growth plate chondrocytes, and can induce exostoses by causing ectopic chondrogenesis of cells on the bone surface. Furthermore, the data are consistent with paracrine signaling from SHP2-deficient cells causing SHP2-sufficient cells to be incorporated into the lesions.
Author Summary
Patients with the inherited disorder, metachondromatosis (MC), develop multiple benign cartilage tumors during childhood. MC patients carry heterozygous loss-of-function mutations in the PTPN11 gene, and their cartilage tumors likely arise when the second PTPN11 allele is lost due to a somatic mutation. PTPN11 encodes a phosphatase called SHP2 that is involved in a variety of signaling pathways. Here, we use mouse models and cell culture assays to investigate the mechanisms by which loss of SHP2 promotes cartilage tumor formation. We show that cartilage tumors that form inside bones (enchondromas) likely arise due to disorganized growth and delayed terminal differentiation of growth plate chondrocytes, while cartilage tumors that form on the bone surface (exostoses) can arise due to ectopic chondrogenesis of fibroblast-like cells that surround bones. We also suggest that paracrine signals from SHP2-deficient cells cause neighboring SHP2-sufficient cells to contribute to exostoses and enchondromas. Finally, we provide in vitro data that the ERK1/2 pathway is regulated by SHP2 and promotes chondrocyte terminal differentiation. Together, our data provide insight into the mechanisms underlying cartilage tumor formation and implicate SHP2 as a key regulator of chondrocyte specification, organization and maturation.
doi:10.1371/journal.pgen.1004364
PMCID: PMC4038465  PMID: 24875294
10.  Enchondromatosis: insights on the different subtypes 
Enchondromatosis is a rare, heterogeneous skeletal disorder in which patients have multiple enchondromas. Enchondromas are benign hyaline cartilage forming tumors in the medulla of metaphyseal bone. The disorder manifests itself early in childhood without any significant gender bias. Enchondromatosis encompasses several different subtypes of which Ollier disease and Maffucci syndrome are most common, while the other subtypes (metachondromatosis, genochondromatosis, spondyloenchondrodysplasia, dysspondyloenchondromatosis and cheirospondyloenchondromatosis) are extremely rare. Most subtypes are non-hereditary, while some are autosomal dominant or recessive. The gene(s) causing the different enchondromatosis syndromes are largely unknown. They should be distinguished and adequately diagnosed, not only to guide therapeutic decisions and genetic counseling, but also with respect to research into their etiology. For a longtime enchondromas have been considered a developmental disorder caused by the failure of normal endochondral bone formation. With the identification of genetic abnormalities in enchondromas however, they were being thought of as neoplasms. Active hedgehog signaling is reported to be important for enchondroma development and PTH1R mutations have been identified in ∼10% of Ollier patients. One can therefore speculate that the gene(s) causing the different enchondromatosis subtypes are involved in hedgehog/PTH1R growth plate signaling. Adequate distinction within future studies will shed light on whether these subtypes are different ends of a spectrum caused by a single gene, or that they represent truely different diseases. We therefore review the available clinical information for all enchondromatosis subtypes and discuss the little molecular data available hinting towards their cause.
PMCID: PMC2907117  PMID: 20661403
Ollier disease; Maffucci syndrome; enchondroma; metachondromatosis; enchondromatosis; central chondrosarcoma
11.  THE INFLUENCE OF AGE AND OF DURATION OF TREATMENT ON THE PRODUCTION AND REPAIR OF BONE LESIONS IN EXPERIMENTAL HYPERPARATHYROIDISM 
These studies have shown that the bones of guinea pigs given daily injections of parathormone from the age of 2 to 7 days to the age of 110 to 120 days, show relatively very little effect after receiving 20 units daily during the last 65 to 87 days of treatment. But it is probable that their bones underwent decalcification early in the treatment and that subsequently the parathormone, continued at the same dosage, did not maintain the effects on the bones. Healing finally occurred despite it. The bones of guinea pigs treated with intermittent injections of large doses of parathormone from the time they were 1 week old to the age of 95 to 145 days also showed relatively few changes at the end of the treatment. The injections were given at intervals of 7 to 11 days, and were stepped up from 60 units to 140 units. From our previous experience (1) we infer that the earlier injections of parathormone produced very extensive bone changes which healed in the intervals between the injections. As the guinea pigs became older the injections of parathormone did not produce as severe effects. We have found in our studies of experimental hyperparathyroidism that the bone changes after a single large dose of parathormone in young guinea pigs are soon healed. The study of a series of animals shows that healing begins at about the 48th hour after injection, and proceeds rapidly. Between the 8th and 14 days, callus may be observed at the costochondral junctions, where fractures had occurred. Now the endosteum may be lined by osteoblasts and the vessel canals by new formed bone. In adult guinea pigs extremely large single doses had little effect on the bones in 48 hours, even though the dose killed the animal. It was only when three doses pyramided over a period of 48 hours and totaling 2580 units of parathormone were given, that moderately severe bone resorption could be demonstrated in the adult. The elevation of serum calcium may be considered as one of the indices of calcium mobilization in experimental hyperparathyroidism. When the rate of calcium excretion exceeds the rate of its mobilization, or when the animal is on a low calcium diet, hypercalcemia may be absent. It is possible to raise the serum calcium of adult guinea pigs by large single doses of parathormone, but the resulting rise is not as great as in the young (2). This is confirmatory evidence of the fact that calcium is mobilized much less rapidly from the bones of old animals than from those of young ones. Collip pointed out that young normal dogs are more susceptible to parathormone (6). This observation was corroborated by Morgan and Garrison (7). We found that the same difference held also in experimental hyperparathyroidism produced in dogs by repeated doses of parathormone (8). In man, clinical experience likewise indicates the necessity of using relatively large doses of parathormone to raise the serum calcium of adults. The serum calcium of middle-aged or old adults does not rise significantly unless as much as 100 units or more of parathormone are given daily for a number of days. Charts VI and VII, in a recent paper by Merritt and Bauer (9), support our findings of the relative difficulty of obtaining a significant elevation of serum calcium in adults. If adult guinea pigs are given daily injections of parathormone which are rapidly stepped up, the animals may be killed by the ensuing acute hyperparathyroidism, only slight bone changes being produced. However, a careful avoidance of the induction of acute hyperparathyroidism by gradual stepping up of the parathormone dose permits the employment of doses continued over a long period of time that could not possibly have been tolerated otherwise. Furthermore, healing of the lesions thus produced may occur, in spite of the continuance of parathormone at this level. It seems likely that the difference in response of young and old guinea pigs to single doses of parathormone, as indicated by the bone changes, as well as by the serum calcium and phosphorus, is related to the more rapid rate of mineral metabolism in the young, actively growing animals. The calcium mobilizing effect of parathormone is most prominent in actively growing young animals, the calcium being withdrawn from the most readily available stores—the regions of most active new bone formation and most active bone reconstruction (10). In the adult animal the calcium reserves (in the formed bone) are less susceptible to the calcium mobilizing effect of parathormone. The adult guinea pig will show relatively slight bone changes even as a result of extremely large, fatal doses of parathormone. Repeated doses, as is well known, will produce, by pyramiding, greater effects than the entire amount administered at one time. In this type of experiment the young again show greater susceptibility of the bone than the adult. In time, however, some compensation takes place, and the effects of the same doses are decreased until finally healing may occur in spite of the continued treatment. Increase of the dose, however, again elicits the parathormone effects upon the bone, as well as upon the serum calcium and phosphorus, without toxic changes (1, 8). It would seem that some compensation sets in which may be overcome by increasing the dose. This compensation is especially evident in the experiments in which the parathormone doses were stepped up gradually from small amounts. In addition to the compensation observed in young and adult animals as a result of repeated injections of parathormone, we must also consider the possibility that there is a compensating mechanism in adult animals more effective than in the young. That compensation occurs is unquestionable but its nature is not clear. Apparently it is less effective during pregnancy, doses of parathormone which produce only slight bone changes in ordinary adults causing very severe lesions in advanced pregnancy (11). Parathormone has been shown to produce only one primary effect on bone, and that is decalcification. This may come about as the result of a change in the circulating tissue fluids, the salts being dissolved out of the organic matrix, and the latter disappearing secondarily. The process is most rapid in the vicinity of most active bone formation. The osteoblasts disappear from the surfaces of bone where dissolution is occurring, and at the same time the marrow connective tissue proliferates. Fusion of cells produces osteoclasts (12), which then proceed to remove the decalcified organic matrix, with the production of the deep lacunae of Howship. Frequently leucocytes are also observed actively phagocyting the decalcified organic matrix, and often leucocytes are observed within the osteoclasts (12). Healing is associated with the complete reversal of the process. The osteoclasts disappear, the connective tissue diminishes, osteoblasts reappear, and bone formation is resumed. As we have previously stated (13), parathormone produces a more continuous effect than experimental acidosis and greater changes than are seen in experimental osteoporosis. A pronounced decalcification results from it which, with its sequelae, simulates von Recklinghausen's disease. The emphasis which the older pathologists laid on osteoclasts as a special feature of ostitis fibrosa cystica is justified, for in the experimental condition the appearance of great numbers of osteoclasts is a constant feature, whenever decalcification occurs (13). There seems to be no doubt that the giant cell tumors found in ostitis fibrosa cystica are expressions of the same pathological response. The other features of the bone changes of hyperparathyroidism—marrow hemorrhage, cysts, fractures, and osteoid proliferation—are secondary to the primary decalcification. Progress of the pathological changes leads to circulatory stasis and cyst formation. Stresses and strains exerted on the progressively weakening bone may result in microscopical or gross fractures. Osteoid tissue is, as we have previously pointed out (13), merely reparative in nature, being laid down as support to the weakened or fractured bone, or as a part of healing. Osteoid borders appear on bone surfaces 48 hours after one large dose of parathormone. The mosaic picture which we have observed in the bones of some of our animals is produced by short and irregularly disposed cement lines resulting from rapid bone transformation. Schmorl (14) recently emphasized the mosaic-like appearance of the newly formed lamellar bone in Paget's disease (ostitis fibrosa deformans). The mosaic-like appearance of bone has also been described in local bone conditions, as e.g. syphilitic periostitis, and in bone in the vicinity of cysts and giant cell tumors in von Recklinghausen's disease (ostitis fibrosa cystica). However, Schmorl claims that in no disease is the mosaic appearance so constant and the arrangement of the cement lines so irregular as in Paget's disease. In chronic experimental hyperparathyroidism (von Recklinghausen's disease), the mosaic structure is not a prominent feature because of the progressive decalcification. But the bones of our young guinea pigs which received intermittent injections showed a mosaic-like appearance indicative of the periodic decalcifications and restorations which they had undergone.
PMCID: PMC2132070  PMID: 19869973
12.  Perichondrium phenotype and border function are regulated by Ext1 and heparan sulfate in developing long bones: A mechanism likely deranged in Hereditary Multiple Exostoses 
Developmental biology  2013;377(1):100-112.
During limb skeletogenesis the cartilaginous long bone anlagen and their growth plates become delimited by perichondrium with which they interact functionally. Yet, little is known about how, despite being so intimately associated with cartilage, perichondrium acquires and maintains its distinct phenotype and exerts its border function. Because perichondrium becomes deranged and interrupted by cartilaginous outgrowths in Hereditary Multiple Exostoses (HME), a pediatric disorder caused by EXT mutations and consequent heparan sulfate (HS) deficiency, we asked whether EXT genes and HS normally have roles in establishing its phenotype and function. Indeed, conditional Ext1 ablation in perichondrium and lateral chondrocytes flanking the epiphyseal region of mouse embryo long bone anlagen – a region encompassing the groove of Ranvier – caused ectopic cartilage formation. A similar response was observed when HS function was disrupted in long bone anlagen explants by genetic, pharmacological or enzymatic means, a response preceded by ectopic BMP signaling within perichondrium. These treatments also triggered excess chondrogenesis and cartilage nodule formation and overexpression of chondrogenic and matrix genes in limb bud mesenchymal cells in micromass culture. Interestingly, the treatments disrupted the peripheral definition and border of the cartilage nodules in such a way that many nodules overgrew and fused with each other into large amorphous cartilaginous masses. Interference with HS function reduced the physical association and interactions of BMP2 with HS and increased the cell responsiveness to endogenous and exogenous BMP proteins. In sum, Ext genes and HS are needed to establish and maintain perichondrium’s phenotype and border function, restrain pro-chondrogenic signaling proteins including BMPs, and restrict chondrogenesis. Alterations in these mechanisms may contribute to exostosis formation in HME, particularly at the expense of regions rich in progenitor cells including the groove of Ranvier.
doi:10.1016/j.ydbio.2013.02.008
PMCID: PMC3733121  PMID: 23458899
Chondro-perichondrial border; Perichondrium; Heparan sulfate; Ext1; Growth plate; Hereditary multiple exostoses; Groove of Ranvier
13.  Hereditary multiple exostoses: a case report 
Hereditary multiple exostoses (HME) is a dominantly inherited skeletal disorder which alters enchondral bone during growth and is characterized by exostoses of the juxta-epiphyseal regions. These exostoses are benign cartilaginous neoplasms that consist of a pedicle of normal bone covered with proliferating cartilage cells. Pathologic, clinical, and radiographic findings are discussed and a case of a nine-year-old male is reviewed.
Images
PMCID: PMC2485147
hereditary multiple exostoses; painful joints; bony masses; chiropractic
14.  Hereditary multiple exostoses in the hands and fingers: early presentation and early surgical treatment in family members. Case reports 
Hand (New York, N.Y.)  2010;6(2):209-216.
Hereditary multiple exostosis (HME) is a benign condition with multiple bony tumors with cartilage caps (osteochondromas), mainly presenting in the long and flat bones. Usually the presentation for HME is between 2 and 10 years of age and most are seen by 4 years of age (Khan et al. 2009). In this paper, we report a family with three members (father, son, and a daughter) who had very early presentations of HME in the fingers within the first 2 years of age. The son presented with bony nodules at 7 months of age, and he required surgery at 13 months of age for a severe functional deformity of his left ring finger. He also had an unusual histological presentation on his osteochondroma that consists of only subperiosteal cartilage without ossification.
doi:10.1007/s11552-010-9307-3
PMCID: PMC3092885  PMID: 22654707
Hand; Hereditary multiple exostoses; Osteochondroma; Early presentation
15.  Osteogenic Protein-1 for Long Bone Nonunion 
Executive Summary
Objective
To assess the efficacy of osteogenic protein-1 (OP-1) for long bone nonunion.
Clinical Need
Although most fractures heal within a normal period, about 5% to 10% do not heal and are classified as delayed or nonunion fractures. Nonunion and segmental bone loss after fracture, reconstructive surgery, or lesion excision can present complex orthopedic problems, and the multiple surgical procedures often needed are associated with patient morbidity and reduced quality of life.
Many factors contribute to the pathogenesis of a delayed union or nonunion fractures, including deficiencies of calcium, vitamin D, or vitamin C, and side effects of medications such as anticoagulants, steroids, some anti-inflammatory drugs, and radiation. It has been shown that smoking interferes with bone repair in several ways.
Incidence of Nonunion and Delayed Union Cases
An estimated 5% to 10% of fractures do not heal properly and go on to delayed union or nonunion. If this overall estimate of incidence were applied to the Ontario population1, the estimated number of delayed union or nonunion in the province would be between 3,863 and 7,725.
Treatment of Nonunion Cases
The treatment of nonunion cases is a challenge to orthopedic surgeons. However, the basic principle behind treatment is to provide both mechanical and biological support to the nonunion site.
Fracture stabilization and immobilization is frequently used with the other treatment modalities that provide biological support to the fractured bone. Biological support includes materials that could be served as a source of osteogenic cells (osteogenesis), a stimulator of mesenchymal cells (osteoinduction), or a scaffold-like structure (osteoconduction).
The capacity to heal a fracture is a latent potential of the stromal stem cells, which synthesize new bone. This process has been defined as osteogenesis. Activation of the stem cells to initiate osteogenic response and to differentiate into bone-forming osteoblasts is called osteoinduction. These 2 properties accelerate the rate of fracture healing or reactivate the ineffective healing process. Osteoconduction occurs when passive structures facilitate the migration of osteoprogenitor cells, the perivascular tissue, and capillaries into these structures.
Bone Grafts and Bone Graft Substitutes
Bone graft and bone graft substitutes have one or more of the following components:
Undifferentiated stem cells
Growth factors
Structural lattice
Undifferentiated stem cells are unspecialized, multipotential cells that can differentiate into a variety of specialized cells. They can also replicate themselves. The role of stem cells is to maintain and repair the tissue in which they are residing. A single stem cell can generate all cell types of that tissue. Bone marrow is a source of at least 2 kinds of stem cells. Hematopoietic stem cells that form all types of blood cells, and bone marrow stromal stem cells that have osteogenic properties and can generate bone, cartilage, and fibrous tissue.
Bone marrow has been used to stimulate bone formation in bone defects and cases of nonunion fractures. Bone marrow can be aspirated from the iliac crest and injected percutaneously with fluoroscopic guidance into the site of the nonunion fracture. The effectiveness of this technique depends on the number and activity of stem cells in the aspirated bone marrow. It may be possible to increase the proliferation and speed differentiation of stem cells by exposing them to growth factor or by combining them with collagen.
Many growth factors and cytokines induced in response to injury are believed to have a considerable role in the process of repair. Of the many bone growth factors studied, bone morphogenetics (BMPs) have generated the greatest attention because of their osteoinductive potential. The BMPs that have been most widely studied for their ability to induce bone regeneration in humans include BMP-2 and BMP-7 (osteogenic protein). Human osteogenic protein-1 (OP-1) has been cloned and produced with recombinant technology and is free from the risk of infection or allergic reaction.
The structural lattice is osteoconductive; it supports the ingrowth of developing capillaries and perivascular tissues. Three distinct groups of structural lattice have been identified: collagen, calcium sulphate, and calcium phosphate. These materials can be used to replace a lost segment of bone.
Grafts Used for Nonunion
Autologous bone graft is generally considered the gold standard and the best material for grafting because it contains several elements that are critical in promoting bone formation, including osteoprogenitor cells, the matrix, and bone morphogenetic proteins. The osteoconductive property of cancellous autograft is related to the porosity of bone. The highly porous, scaffold-like structure of the graft allows host osteoblasts and host osteoprogenitor cells to migrate easily into the area of the defect and to begin regeneration of bone. Sources of cancellous bone are the iliac crest, the distal femur, the greater trochanter, and the proximal tibia. However, harvesting the autologous bone graft is associated with postoperative pain at the donor site, potential injury to the surrounding arteries, nerves, and tissues, and the risk of infection. Thus the development of synthetic materials with osteoconductive and osteoinductive properties that can eliminate the need for harvesting has become a major goal of orthopedic research.
Allograft is the graft of tissue between individuals who are of the same species but are of a disparate genotype. Allograft has osteoconductive and limited osteoinductive properties. Demineralized bone matrix (DBM) is human cortical and cancellous allograft. These products are prepared by acid extraction of allograft bone, resulting in the loss of most of the mineralized component while collagen and noncollagenous proteins, including growth factors, are retained. Figures 1 to 5 demonstrate the osteogenic, osteoinduction, and osteoconduction properties of autologous bone graft, allograft, OP-1, bone graft substitutes, and bone marrow.
Autologous Bone Graft
Osteogenic Protein-1
Allograft bone and Demineralized Bone Matrix
Bone Graft Substitutes
Autologous Bone Marrow Graft
New Technology Being Reviewed: Osteogenic Protein-1
Health Canada issued a Class IV licence for OP-1 in June 2004 (licence number 36320). The manufacturer of OP-1 is Stryker Biotech (Hapkinton, MA).
The United States Food and Drug Administration (FDA) issued a humanitarian device exemption for the application of the OP-1 implant as an “alternative to autograft in recalcitrant long bone nonunions where use of autograft is unfeasible and alternative treatments have failed.” Regulatory agencies in Europe, Australia, and New Zealand have permitted the use of this implant in specific cases, such as in tibial nonunions, or in more general cases, such as in long bone nonunions.
According to the manufacturer, OP-1 is indicated for the treatment of long bone nonunions. It is contraindicated in the patient has a hypersensitivity to the active substance or collagen, and it should not be applied at the site of a resected tumour that is at or near the defect or fracture. Finally, it should not be used in patients who are skeletally immature (< 18 years of age), or if there is no radiological evidence of closure of epiphysis.
Review Strategy
Objective
To summarize the safety profile and effectiveness of OP-1 in the treatment of cases of long bone nonunion and bone defects
To compare the effectiveness and cost effectiveness of OP-1 in the treatment of long bone nonunions and bone defects with the alternative technologies, particularly the gold standard autologous bone graft.
Literature Search
International Network of Agencies for Health Technology Assessments (INAHTA), the Cochrane Database of Systematic Reviews and the CCTR (formerly Cochrane Controlled Trials Register) were searched for health technology assessments. MEDLINE, EMBASE, Medline In Process and Other Non-Indexed Citations were searched from January 1, 1996 to January 27, 2004 for studies on OP-1. The search was limited to English-language articles and human studies. The search yielded 47 citations. Three studies met inclusion criteria (2 RCTs and 1 Ontario-based study presented at an international conference.
Summary of Findings
Friedlaender et al. conducted a prospective, randomized, partially blinded clinical trial on the treatment tibial nonunions with OP-1. Tibial nonunions were chosen for this study because of their high frequency, challenging treatment requirements, and substantial morbidity. All of the nonunions were at least 9 months old and had shown no progress toward healing over the previous 3 months. The patients were randomized to receive either treatment with autologous bone grafting or treatment with OP-1 in a type-1 collagen carrier. Both groups received reduction and fixation with an intramedullary rod. Table 1 summarizes the clinical outcomes of this study.
Outcomes in a Randomized Clinical Trial on Tibial Nonunions: Osteogenic Protein-1 versus Autologous Bone Grafting
Clinical success was defined as full weight-bearing, loss of severe pain at the fracture site on weight-bearing, and no further surgical treatment to enhance fracture repair.
The results of this study demonstrated that recombinant OP-1 is associated with substantial clinical and radiographic success for the treatment of tibial nonunions when used with intramedullary rod fixation. No adverse event related to sensitization was reported. Five per cent of the patients in the OP-1 group had circulating antibodies against type 1 collagen. Only 10% of the patients had a low level of anti-OP-1 antibodies, and all effects were transient. Furthermore, the success rate with the OP-1 implant was comparable with those achieved with autograft at 9 and 24 months follow-up. Eighty-two per cent of patients were successful at 24 months follow-up in both groups.
Statistically significant increased blood loss in the group treated with the autograft was observed (P = .049). Patients treated with autograft had longer operation and hospitalization times. All patients in the autograft group had pain at the donor site after surgery, and more than 80% judged their postoperative pain as moderate or severe. At their 6-month visit, 20% of the patients in the autograft group had persistent pain, mild or moderate in nature, at the donor site. This number fell to 13% at 12 months.
All patients in each of the groups had at least 1 adverse event that wasn’t serious, such as fever, nausea and vomiting, leg edema, discomfort, and bruising at the operative site. The incidence of these events was similar in both groups. Serious adverse events were observed in 44% of both groups, none of which were considered related to the OP-1 implant or autograft.
On the basis of this data, the FDA issued a humanitarian device exemption for the application of OP-1 implant as an alternative to autograft in recalcitrant long bone nonunions when the use of autograft is unfeasible and alternative treatments have failed.
Study on Fibular Defects
Geesink et al. investigated the osteogenic activity of OP-1 by assessing its value in bridging fibular defects made at the time of tibial osteotomy for varus or valgus deformity of the knee. This study had 2 phases and included 12 patients in each phase. Each phase included 12 patients (6 in each group). Patients in the first phase received either DBM or were left untreated. Patients in the second phase received either OP-1 on collagen type-1 or collagen type-1 alone.
Radiological and Dual Energy X-ray Absorptiometry (DEXA) evaluation showed that in patients in whom the defect was left untreated, no formation of bone occurred. At 12 months follow-up, new bone formation with bridging occurred in 4 of the 6 patients in DMB group, and 5 of the 6 patients in OP-1 group. One patient in OP-1 group did not show any evidence of new bone formation at any point during the study.
Ontario Pilot Study
A prospective pilot study was conducted in Ontario, Canada to investigate the safety and efficacy of OP-1 for the treatment of recalcitrant long bone nonunions. The study looked at 15 patients with complex, recalcitrant, long bone nonunions whose previous treatment had failed. The investigators concluded that this bone graft substitute appears to be safe and effective in providing sufficient biological stimulation in difficult to treat nonunions. Results of a more complete study on 70 patients are ready for publication. According to the principal investigator, OP-1 was 90% effective in inducing bone formation and bone healing in this sample.
Alternative Technologies
The Medical Advisory Secretariat conducted a literature search from January 1, 2000 to February 28, 2005 to identify studies on nonunions/bone defects that had been treated with alternative technologies. A review of these studies showed that, in addition to the gold standard autologous bone marrow grafting, bone allografts, demineralized bone matrices, bone graft substitutes, and autologous bone marrow have been used for treatment of nonunions and bone defects. These studies were categorized according to the osteoinductive, osteoconductive, and osteogenesis properties of the technologies studied.
A review of these studies showed that bone allografts have been used mostly in various reconstruction procedures to restore the defect after excavating a bone lesion. Two studies investigated the effectiveness of DBM in healing fracture nonunions. Calcium phosphate and calcium sulphate have been used mostly for repair of bone defects.
Several investigators have looked at the use of autologous bone marrow for treatment of long bone nonunions. The results of these studies show that method of percutaneous bone marrow grafting is highly effective in the treatment of long bone nonunions. In a total of 301 fractures across all studies, 268 (89%) healed with a mean healing time of 2.5 to 8 months. This healing time as derived from these case series is less than the timing of the primary end point in Friedlaender’s study (9 months). Table 2 summarizes the results of these studies. Table 2 summarizes the results of these studies.
Studies that used Percutaneous Bone Marrow Grafting for Treatment of Nonunions
Economic Analysis
Based on annual estimated incidence of long-bone nonunion of 3,863 - 7,725, the annual hospitalization costs associated with this condition is between $21.2 and $42.3 million based on a unit cost of $5,477 per hospital separation. When utilized, the device, a single vial of OP-1, is approximately $5,000 and if adopted universally in Ontario, the total device costs would be in the range of $19.3 - $38.6 million annually. The physician fee for harvest, insertion of bone, or OP-1 is $193 and is $193 for autologous bone marrow transplantation. Total annual physician costs are expected to be in the range of from $0.7 million to $1.3 million per year. Expenditures associated with long-bone nonunion are unlikely to increase since incidence of long-bone nonunion is unlikely to change in the future. However, the rate of uptake of OP-1 could have a significant impact on costs if the uptake were large.
The use of OP-1 and autologous bone marrow transplantation may offset pain medication costs compared with those associated with autologous bone harvest given that the former procedures do not involve the pain associated with the bone harvest site. However, given that this pain is normally not permanent, the overall offset is likely to be small. There are likely to be smaller OHIP costs associated with OP-1 than bone-harvest procedures given that only 1, rather than 2, incisions are needed when comparing the former with the latter procedure. This offset could amount to between $0.3 million to $0.7 million annually.
No data on the cost-effectiveness of OP-1 is available.
PMCID: PMC3382627  PMID: 23074475
16.  Spinal stenosis frequent in children with multiple hereditary exostoses 
Purpose
Children with multiple hereditary exostoses (MHE) have numerous osteochondromas, with the most prominent lesions typically over the appendicular skeleton. A recent report noted a high rate of intracanal lesions in this patient population and recommended preventative spinal screening with magnetic resonance imaging (MRI) or computed tomography (CT). We sought to evaluate the prevalence of spinal stenosis from intracanal osteochondromas at our pediatric orthopedic center in order to evaluate if routine screening is warranted.
Methods
All pediatric patients treated for MHE were retrospectively identified. Records were reviewed to determine demographics, previous orthopedic surgery, and indication and results of axial spine imaging (CT or MRI). Imaging studies were reviewed to evaluate the presence of intracanal and compressive spinal lesions.
Results
Between 1990 and 2011, axial imaging was performed in nine patients with MHE due to concerns of pain, weakness, and/or dizziness. These patients had moderate disease involvement, with a mean of 4.9 previous orthopedic surgeries to address skeletal osteochondromas. Two patients with MHE had cervical spinal stenosis secondary to intracanal osteochondromas. Both children successfully underwent spinal decompression. Thus, of our MHE population undergoing axial imaging, 22 % were noted to have intracanal lesions.
Conclusions
Our experience reveals a >20 % rate of compressive intracanal osteochondromas in MHE patients undergoing spinal imaging. These two patients represent 5 % of the MHE patients treated at our center. These lesions may be slow growing, and significant consequences can occur if not identified promptly. Thus, we confer that routine axial screening of the spinal canal may be warranted in these children.
doi:10.1007/s11832-013-0484-9
PMCID: PMC3672460  PMID: 24432077
Pediatric; Multiple hereditary exostoses; Neurologic symptoms; Spinal impingement; Imaging; MRI; CT
17.  Vitamin K Supplementation in Postmenopausal Women with Osteopenia (ECKO Trial): A Randomized Controlled Trial 
PLoS Medicine  2008;5(10):1-12.
Background
Vitamin K has been widely promoted as a supplement for decreasing bone loss in postmenopausal women, but the long-term benefits and potential harms are unknown. This study was conducted to determine whether daily high-dose vitamin K1 supplementation safely reduces bone loss, bone turnover, and fractures.
Methods and Findings
This single-center study was designed as a 2-y randomized, placebo-controlled, double-blind trial, extended for earlier participants for up to an additional 2 y because of interest in long-term safety and fractures. A total of 440 postmenopausal women with osteopenia were randomized to either 5 mg of vitamin K1 or placebo daily. Primary outcomes were changes in BMD at the lumbar spine and total hip at 2 y. Secondary outcomes included changes in BMD at other sites and other time points, bone turnover markers, height, fractures, adverse effects, and health-related quality of life. This study has a power of 90% to detect 3% differences in BMD between the two groups. The women in this study were vitamin D replete, with a mean serum 25-hydroxyvitamin D level of 77 nmol/l at baseline. Over 2 y, BMD decreased by −1.28% and −1.22% (p = 0.84) (difference of −0.06%; 95% confidence interval [CI] −0.67% to 0.54%) at the lumbar spine and −0.69% and −0.88% (p = 0.51) (difference of 0.19%; 95% CI −0.37% to 0.75%) at the total hip in the vitamin K and placebo groups, respectively. There were no significant differences in changes in BMD at any site between the two groups over the 2- to 4-y period. Daily vitamin K1 supplementation increased serum vitamin K1 levels by 10-fold, and decreased the percentage of undercarboxylated osteocalcin and total osteocalcin levels (bone formation marker). However, C-telopeptide levels (bone resorption marker) were not significantly different between the two groups. Fewer women in the vitamin K group had clinical fractures (nine versus 20, p = 0.04) and fewer had cancers (three versus 12, p = 0.02). Vitamin K supplements were well-tolerated over the 4-y period. There were no significant differences in adverse effects or health-related quality of life between the two groups. The study was not powered to examine fractures or cancers, and their numbers were small.
Conclusions
Daily 5 mg of vitamin K1 supplementation for 2 to 4 y does not protect against age-related decline in BMD, but may protect against fractures and cancers in postmenopausal women with osteopenia. More studies are needed to further examine the effect of vitamin K on fractures and cancers.
Trial registration: ClinicalTrials.gov (#NCT00150969) and Current Controlled Trials (#ISRCTN61708241)
Angela Cheung and colleagues investigate whether vitamin K1 can prevent bone loss among postmenopausal women with osteopenia.
Editors' Summary
Background.
Osteoporosis is a bone disease in which the bones gradually become less dense and more likely to break. In the US, 10 million people have osteoporosis and 18 million have osteopenia, a milder condition that precedes osteoporosis. In both conditions, insufficient new bone is made and/or too much old bone is absorbed. Although bone appears solid and unchanging, very little bone in the human body is more than 10 y old. Old bone is continually absorbed and new bone built using calcium, phosphorous, and proteins. Because the sex hormones control calcium and phosphorous deposition in the bones and thus bone strength, the leading cause of osteoporosis in women is reduced estrogen levels after menopause. In men, an age-related decline in testosterone levels can cause osteoporosis. Most people discover they have osteoporosis only when they break a bone, but the condition can be diagnosed and monitored using bone mineral density (BMD) scans. Treatments can slow down or reverse bone loss (antiresorptive therapies) and some (bone formation therapies) can even make bone and build bone tissue.
Why Was This Study Done?
Although regular exercise and a healthy diet can help to keep bones strong, other ways of preventing osteoporosis are badly needed. Recently, the lay media has promoted vitamin K supplements as a way to reduce bone loss in postmenopausal women. Vitamin K (which is found mainly in leafy green vegetables) is required for a chemical modification of proteins called carboxylation. This modification is essential for the activity of three bone-building proteins. In addition, there is some evidence that low bone density and fractures are associated with a low vitamin K intake. However, little is known about the long-term benefits or harms of vitamin K supplements. In this study, the researchers investigate whether a high-dose daily vitamin K supplement can safely reduce bone loss, bone turnover, and fractures in postmenopausal women with osteopenia in a randomized controlled trial called the “Evaluation of the Clinical Use of Vitamin K Supplementation in Post-Menopausal Women With Osteopenia” (ECKO) trial.
What Did the Researchers Do and Find?
In the study, 440 postmenopausal women with osteopenia were randomized to receive 5mg of vitamin K1 (the type of vitamin K in North American food; the recommended daily adult intake of vitamin K1 is about 0.1 mg) or an inactive tablet (placebo) daily for 2 y; 261 of the women continued their treatment for 2 y to gather information about the long-term effects of vitamin K1 supplementation. All the women had regular bone density scans of their lower back and hips and were examined for fractures and for changes in bone turnover. After 2 y and after 4 y, lower back and hip bone density measurements had decreased by similar amounts in both treatment groups. The women who took vitamin K1 had 10-fold higher amounts of vitamin K1 in their blood than the women who took placebo and lower amounts of a bone formation marker; the levels of a bone resorption marker were similar in both groups. Over the 4-y period, fewer women in the vitamin K group had fractures (nine versus 20 women in the placebo group), and fewer had cancer (three versus 12). Finally, vitamin K supplementation was well tolerated over the 4-y period and adverse health effects were similar in the two treatment groups.
What Do These Findings Mean?
These findings indicate that a high daily dose of vitamin K1 provides no protection against the age-related decline in bone density in postmenopausal women with osteopenia, but that vitamin K1 supplementation may protect against fractures and cancers in these women. The apparent contradiction between the effects of vitamin K1 on bone density and on fractures could mean that vitamin K1 supplements strengthen bone by changing factors other than bone density, e.g., by changing its fine structure rather than making it denser. However, because so few study participants had fractures, the difference in the fracture rate between the two treatment groups might have occurred by chance. Larger studies are therefore needed to examine the effect of vitamin K1 on fractures (and on cancer) and, until these are done, high-dose vitamin K1 supplementation should not be recommended for the prevention of osteoporosis.
Additional Information.
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0050196.
The US National Institute of Arthritis and Musculoskeletal and Skin Diseases provides detailed information about osteoporosis (in English and Spanish) and links to other resources, including an interactive web tool called Check Up On Your Bones
MedlinePlus provides links to additional information about osteoporosis (in English and Spanish)
The MedlinePlus Encyclopedia has a page about vitamin K
The UK Food Standards Agency provides information about vitamin K
Full details about the ECKO trial are available on the ClinicalTrials.gov Web site
The Canadian Task Force for Preventive Health Care provides recommendations on the prevention of osteoporosis and osteoporotic fractures in postmenopausal women
Osteoporosis Canada provides information on current topics related to osteoporosis
doi:10.1371/journal.pmed.0050196
PMCID: PMC2566998  PMID: 18922041
18.  Intrafamilial clinical variability of type 1 Gaucher disease in a French-Canadian family. 
Journal of Medical Genetics  1988;25(5):322-325.
Glucocerebroside beta-glucosidase (glucocerebrosidase) activity was determined from peripheral blood lymphocytes and cultured skin fibroblasts of eight full sibs in a French-Canadian family at risk for Gaucher disease, an autosomal recessive sphingolipidosis resulting from deficient glucocerebrosidase activity. The diagnosis of type 1, non-neuronopathic Gaucher disease was made in all of the five affected sibs on the basis of deficient (7.5 to 15.5% of control mean) glucocerebrosidase activity and absence of neurological involvement. Normal levels of enzyme activity were found in two of the three asymptomatic sibs. The third asymptomatic sib had an intermediate level (about 50% of control mean) of fibroblast and lymphocyte glucocerebrosidase activity, indicating that he is a carrier. Considerable clinical heterogeneity was noted among the five affected sibs. One patient is mildly affected and so far has not developed any orthopaedic complications associated with Gaucher disease. His haematological complications were also reversed after splenectomy 24 years ago. In contrast to this mild presentation, the patient's splenectomised sister has been very anaemic and thrombocytopenic. There have been severe orthopaedic complications associated with Gaucher disease, including vertebral compression, avascular necrosis, and pathological fracture of the long bones. The clinical picture of the other three affected sibs appeared to vary between the two extremes. Although the asymptomatic parents of the patients died many years ago, their heterozygous status with respect to Gaucher disease can be deduced by the presence of Gaucher homozygotes, normal homozygotes, and one heterozygote among their eight offspring. Present findings suggest that the clinical variability of type 1 Gaucher disease may be attributed to variable expressions of the same Gaucher mutant alleles, in addition to the presence of multiple mutant alleles that are widely disseminated in the population.
PMCID: PMC1050458  PMID: 3385740
19.  Acute Lower Extremity Ischemia due to the Popliteal Pseudoaneurysm in a 16-year-old Boy with Multiple Exostoses 
Annals of Vascular Diseases  2013;6(2):215-217.
Osteochondromas or exostoses are the most common benign bone tumors. This is a case of a 16-year-old boy with multiple osteochondromatosis which caused the popliteal pseudoaneurysm and a subsequent distal embolism. Vascular complications, especially acute limb ischemia, caused by osteochondromas are very rare. This abnormality should be searched for when dealing with young patients with acute limb ischemia.
doi:10.3400/avd.cr.13-00015
PMCID: PMC3692996  PMID: 23825507
multiple exostoses; pseudoaneurysm; vascular complications of exostosis
20.  Hip Fracture Incidence in Relation to Age, Menopausal Status, and Age at Menopause: Prospective Analysis 
PLoS Medicine  2009;6(11):e1000181.
Using data from the UK Million Women Study, Emily Banks and colleagues investigate the relationships between the incidence of hip fracture and a woman's age, menopausal status, and age at menopause.
Background
Bone mineral density is known to decrease rapidly after the menopause. There is limited evidence about the separate contributions of a woman's age, menopausal status and age at menopause to the incidence of hip fracture.
Methods and Findings
Over one million middle-aged women joined the UK Million Women Study in 1996–2001 providing information on their menopausal status, age at menopause, and other factors, which was updated, where possible, 3 y later. All women were registered with the UK National Health Service (NHS) and were routinely linked to information on cause-specific admissions to NHS hospitals. 561,609 women who had never used hormone replacement therapy and who provided complete information on menopausal variables (at baseline 25% were pre/perimenopausal and 75% postmenopausal) were followed up for a total of 3.4 million woman-years (an average 6.2 y per woman). During follow-up 1,676 (0.3%) were admitted to hospital with a first incident hip fracture. Among women aged 50–54 y the relative risk (RR) of hip fracture risk was significantly higher in postmenopausal than premenopausal women (adjusted RR 2.22, 95% confidence interval [CI] 1.22–4.04; p = 0.009); there were too few premenopausal women aged 55 y and over for valid comparisons. Among postmenopausal women, hip fracture incidence increased steeply with age (p<0.001), with rates being about seven times higher at age 70–74 y than at 50–54 y (incidence rates of 0.82 versus 0.11 per 100 women over 5 y). Among postmenopausal women of a given age there was no significant difference in hip fracture incidence between women whose menopause was due to bilateral oophorectomy compared to a natural menopause (adjusted RR 1.20, 95% CI 0.94–1.55; p = 0.15), and age at menopause had little, if any, effect on hip fracture incidence.
Conclusions
At around the time of the menopause, hip fracture incidence is about twice as high in postmenopausal than in premenopausal women, but this effect is short lived. Among postmenopausal women, age is by far the main determinant of hip fracture incidence and, for women of a given age, their age at menopause has, at most, a weak additional effect.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
Anyone can break a hip but most hip fractures occur in elderly people. As people age, their bones gradually lose minerals and become less dense, which weakens the bones and makes them more susceptible to fracture. Because women lose bone density faster than men as they age and because women constitute the majority of the elderly, three-quarters of hip fractures occur in women. Hip fractures can cause long-term health problems and premature death. Thus, although surgical repair of a broken hip usually only requires a hospital stay of about a week, a quarter of elderly people who were living independently before their fracture have to stay in a nursing home for at least a year after their injury and a fifth of elderly people who break a hip die within the year. Most hip fractures are caused by falls. Regular exercise to improve strength and balance combined with review of medicines (to reduce side effects and interactions), regular eye examinations, and the removal of fall hazards from the home can help to prevent hip fractures in elderly people.
Why Was This Study Done?
Bone density decreases very rapidly in women immediately after menopause—the time when menstruation permanently stops—and then continues to decrease more slowly with age. Most women have their menopause in their early 50s but menopause can occur in younger women. Early menopause is thought to be a risk factor for osteoporosis (thinning of the bones) and fractures later in life but little is known about how menopause influences hip fracture risk as women age. In this prospective study (a type of study in which a group of people is followed for several years to see whether they develop a particular condition), the researchers investigate the incidence of hip fractures in relation to age, menopausal status, and age at menopause among the participants of the Million Women Study. This study, which recruited 1.3 million women aged 50–64 years who attended UK breast cancer screening clinics between 1996 and 2001, has been investigating how reproductive and lifestyle factors affect women's health.
What Did the Researchers Do and Find?
At enrollment and three years later, the study participants provided information about their menopausal status and other health and lifestyle factors likely to affect their fracture risk. From these data, the researchers identified more than half a million women who had never used hormone replacement therapy (which reduces fracture risk) and who had given complete information about their menopausal status. They then looked for statistical associations between the occurrence of a first hip fracture in these women over the next few years and their age, menopausal status, and age at menopause. Among women aged 50–54 years, postmenopausal women were twice as likely to have a hip fracture as premenopausal women. Among postmenopausal women, the incidence of hip fractures increased steeply with age and was seven times higher in 70–74-year olds than in 50–54-year olds. Women who had their menopause before age 45 had a slightly increased risk of hip fracture but any effect of age at menopause on the risk of hip fracture was small compared to the effect of age itself, and the slightly increased risk may have been due to other factors that could not be fully accounted for in the analysis.
What Do These Findings Mean?
These findings indicate that around the time of menopause, although hip fractures are rare, the risk of a fracture in postmenopausal women is twice that in premenopausal women. The findings also show that among postmenopausal women, age is the major determinant of hip fracture risk and that for women of a given age, their age at menopause has little effect on hip fracture risk. Women attending breast cancer screening clinics and completing questionnaires about their health may not be representative of the general population. Furthermore, these findings rely on women self-reporting their menopausal status accurately. Nevertheless, the results of this study suggest that clinicians advising women about hip fracture prevention should probably base their advice on the woman's age and on age-related factors such as frailty rather than on factors related to menopause. Clinicians can also now reassure elderly women who had an early menopause that their risk of hip fracture is unlikely to be higher than that of similar women who had a later menopause.
Additional Information
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1000181.
The American Academy of Orthopaedic Surgeons has detailed information about hip fractures
The US National Institute of Arthritis and Muscoloskeletal and Skin Diseases has an interactive feature called “Check up on your bones and provides detailed information about osteoporosis, including advice on fall prevention
The US Centers for Disease Control and Prevention has a fact sheet about hip fractures among older adults
MedlinePlus has links to resources about hip fracture, osteoporosis, and menopause (in English and Spanish)
More information on the Million Women Study is available
doi:10.1371/journal.pmed.1000181
PMCID: PMC2766835  PMID: 19901981
21.  Mice deficient in Ext2 lack heparan sulfate and develop exostoses 
Development (Cambridge, England)  2005;132(22):5055-5068.
Summary
Hereditary multiple exostoses (HME) is a genetically heterogeneous human disease characterized by the development of bony outgrowths near the ends of long bones. HME results from mutations in EXT1 and EXT2, genes that encode glycosyltransferases that synthesize heparan sulfate chains. To study the relationship of the disease to mutations in these genes, we generated Ext2-null mice by gene targeting. Homozygous mutant embryos developed normally until embryonic day 6.0, when they became growth arrested and failed to gastrulate, pointing to the early essential role for heparan sulfate in developing embryos. Heterozygotes had a normal lifespan and were fertile; however, analysis of their skeletons showed that about one-third of the animals formed one or more ectopic bone growths (exostoses). Significantly, all of the mice showed multiple abnormalities in cartilage differentiation, including disorganization of chondrocytes in long bones and premature hypertrophy in costochondral cartilage. These changes were not attributable to a defect in hedgehog signaling, suggesting that they arise from deficiencies in other heparan sulfate-dependent pathways. The finding that haploinsufficiency triggers abnormal cartilage differentiation gives insight into the complex molecular mechanisms underlying the development of exostoses.
doi:10.1242/dev.02088
PMCID: PMC2767329  PMID: 16236767
Homologous recombination; Knockout; Hypertrophic cartilage; Chondrocyte; Hereditary multiple exostoses; Heparan sulfate; Mouse
22.  Multiple Mandibular Exostoses: A Rare Case Report 
Multiple maxillary and mandibular exostoses are common localized overgrowths of the bone. They are non-neoplastic and are thought to be reactive or developmental in origin. These exostoses need to be accurately distinguished from the other more diagnostically significant lesions, notably from the exosteal osteomas. The aetiology of exostosis has been investigated by different authors, but no consensus has been reached so far. We are reporting a rare case of an otherwise healthy 38 year old female with multiple exostoses in the mandibular anterior region, which correlated both clinically and radiographically.
doi:10.7860/JCDR/2013/5612.3283
PMCID: PMC3782976  PMID: 24086919
Multiple exostoses; Osteoma
23.  Secondary Chondrosarcoma of the Lumbosacral Region: Are any Bones Spared in the Multiple Hereditary Exostoses? 
Osteochondromas are the most common benign bone tumors. Usually solitary, multiple osteochondromas (exostoses) are seen in patients with Multiple Hereditary Exostoses (MHE). Chondromatous transformation of lumbar osteochondroma in a patient with multiple exostoses is a rare phenomenon. We present a rare case of secondary chondrosarcoma of lumbar exostoses with patient presenting with symptoms of pain in the right lumbar region and paresis of right lower limb. Patients with multiple exostoses are prone to develop chondrosarcoma early in life. These patients need long term follow up with regular clinical and radiological examination.
doi:10.7860/JCDR/2012/4241.2611
PMCID: PMC3552228  PMID: 23373052
Osteochondroma; Multiple Hereditary Exosostosis; Secondary Lumbar Chondrosarcoma
24.  The gene for hereditary multiple exostoses does not map to the Langer-Giedion region (8q23-q24). 
Journal of Medical Genetics  1992;29(10):713-715.
Hereditary multiple exostoses is a dominantly inherited skeletal disorder which alters enchondral bone during growth and is characterised by exostoses of the juxta-epiphyseal regions. Using polymorphic DNA probes, we have been able to exclude the disease gene from close proximity to the 8q24.1 region where a dominant syndrome with multiple exostoses, the trichorhinophalangeal syndrome type II (TRP II, Langer-Giedion syndrome, MIM 15025), has been previously localised (pairwise linkage Z = -8.96 at theta = 0 with probe L48 at locus D8S51). Multipoint linkage analysis using probes L48, L24, and L1 consistently excluded the HME gene from a large area of the distal long arm of chromosome 8, spanning the smallest region of overlap assigned to the TRP II gene. These studies support the clinical view that HME and TRP II are distinct entities.
Images
PMCID: PMC1016129  PMID: 1433231
25.  Genotype-phenotype correlation in hereditary multiple exostoses 
Journal of Medical Genetics  2001;38(7):430-434.
Hereditary multiple exostoses (HME) is a genetically heterogeneous autosomal dominant disorder characterised by the development of bony protuberances mainly located on the long bones. Three HME loci have been mapped to chromosomes 8q24 (EXT1), 11p11-13 (EXT2), and 19p (EXT3). The EXT1 and EXT2 genes encode glycosyltransferases involved in biosynthesis of heparan sulphate proteoglycans. Here we report on a clinical survey and mutation analysis of 42 HME French families and show that EXT1 and EXT2 accounted for more than 90% of HME cases in our series. Among them, 27/42 cases were accounted for by EXT1 (64%, four nonsense, 19 frameshift, three missense, and one splice site mutations) and 9/42 cases were accounted for by EXT2 (21%, four nonsense, two frameshift, two missense, and one splice site mutation). Overall, 31/36 mutations were expected to cause loss of protein function (86%). The most severe forms of the disease and malignant transformation of exostoses to chondrosarcomas were associated with EXT1 mutations. These findings provide the first genotype-phenotype correlation in HME and will, it is hoped, facilitate the clinical management of these patients.


Keywords: hereditary multiple exostoses; EXT1; EXT2; chondrosarcoma
doi:10.1136/jmg.38.7.430
PMCID: PMC1757186  PMID: 11432960

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