Mutations of fibroblast growth factor receptor 2 (FGFR2) account for a higher proportion of genetic cases of craniosynostosis than any other gene, and are associated with a wide spectrum of severity of clinical problems. Many of these mutations are highly recurrent and their associated features well documented. Crouzon syndrome is typically caused by heterozygous missense mutations in the third immunoglobulin domain of FGFR2.
Here we describe two families, each segregating a different, previously unreported FGFR2 mutation of the same nucleotide, c.1083A>G and c.1083A>T, both of which encode an apparently synonymous change at the Pro361 codon. We provide experimental evidence that these mutations affect normal FGFR2 splicing and document the clinical consequences, which include a mild Crouzon syndrome phenotype and reduced penetrance of craniosynostosis.
These observations add to a growing list of FGFR2 mutations that affect splicing and provide important clinical information for genetic counselling of families affected by these specific mutations.
Craniosynostosis; Crouzon syndrome; Expressivity; FGFR2; Penetrance; Splicing; Synonymous substitution
The Loeys-Dietz syndrome (LDS) is a rare autosomal dominant disorder characterized by thoracic aortic aneurysm and dissection and widespread systemic connective tissue involvement. LDS type 1 to 4 are caused by mutations in genes of the TGF-β signaling pathway: TGFBR1 and TGFBR2 encoding the TGF-β receptor (LDS1 and LDS2), SMAD3 encoding the TGF-β receptor cytoplasmic effector (LDS3), and TGFB2 encoding the TGF-β2 ligand (LDS4). LDS4 represents the mildest end of the LDS spectrum, since aneurysms are usually observed in fourth decade and the progression of the disease is slower than in the other forms.
We report the clinical and molecular findings of an LDS4 Italian family. Genetic testing included TGFBR1, TGFBR2, SMAD3, and TGFB2 analysis by Sanger sequencing. In order to verify the effect of the identified splice mutation, RT-PCR analysis was performed.
The proband, a 57-year-old woman, showed high palate, hypoplasic uvula, easy bruising, joint hypermobility, chronic pain, scoliosis, multiple relapsing hernias, dural ectasia, and mitral valve prolapse. Magnetic resonance angiography revealed tortuosity and ectasia of carotid, vertebral, cerebral, and segmental pulmonary arteries. Arterial aneurysm and dissection never occurred. Her 39- and 34-year-old daughters presented with a variable degree of musculoskeletal involvement. Molecular analysis disclosed the novel c.839-1G>A splice site mutation in the TGFB2 gene. This mutation activates a cryptic splice acceptor site in exon 6 leading to frameshift, premature termination codon and haploinsufficiency (p.Gly280Aspfs*41).
Our data confirm that loss-of-function mutations in TGFB2 gene do not always lead to aggressive vascular phenotypes and that articular and skeletal signs are prevalent, therefore suggesting that LDS4 must be considered in patients with sparse signs of LDS and related disorders also in the absence of vascular events.
Loeys-Dietz syndrome type 4; TGFB2; TGF-ß2; Splicing mutation
Wolfram Syndrome type 2 (WFS2) is considered a phenotypic and genotypic variant of WFS, whose minimal criteria for diagnosis are diabetes mellitus and optic atrophy. The disease gene for WFS2 is CISD2. The clinical phenotype of WFS2 differs from WFS1 for the absence of diabetes insipidus and psychiatric disorders, and for the presence of bleeding upper intestinal ulcers and defective platelet aggregation. After the first report of consanguineous Jordanian patients, no further cases of WFS2 have been reported worldwide. We describe the first Caucasian patient affected by WFS2.
The proband was a 17 year-old girl. She presented diabetes mellitus, optic neuropathy, intestinal ulcers, sensorineural hearing loss, and defective platelet aggregation to ADP. Genetic testing showed a novel homozygous intragenic deletion of CISD2 in the proband. Her brother and parents carried the heterozygous mutation and were apparently healthy, although they showed subclinical defective platelet aggregation. Long runs of homozygosity analysis from SNP-array data did not show any degree of parental relationship, but the microsatellite analysis confirmed the hypothesis of a common ancestor.
Our patient does not show optic atrophy, one of the main diagnostic criteria for WFS, but optic neuropathy. Since the “asymptomatic” optic atrophy described in Jordanian patients is not completely supported, we could suppose that the ocular pathology in Jordanian patients was probably optic neuropathy and not optic atrophy. Therefore, as optic atrophy is required as main diagnostic criteria of WFS, it might be that the so-called WFS2 could not be a subtype of WFS. In addition, we found an impaired aggregation to ADP and not to collagen as previously reported, thus it is possible that different experimental conditions or inter-patient variability can explain different results in platelet aggregation. Further clinical reports are necessary to better define the clinical spectrum of this syndrome and to re-evaluate its classification.
CISD2; Optic neuropathy; Non-autoimmune diabetes mellitus; Novel mutation; Platelet aggregation; Sensorineural hearing loss; SNP-array; Upper intestinal ulcers; Wolfram syndrome
SHOX alterations have been reported in 67% of patients affected by Léri-Weill dyschondrosteosis (LWD), with a larger prevalence of gene deletions than point mutations. It has been recently demonstrated that these deletions can involve the SHOX enhancer region, rather that the coding region, with variable phenotype of the affected patients.
Here, we report a SHOX gene analysis carried out by MLPA in 14 LWD patients from 4 families with variable phenotype.
All patients presented a SHOX enhancer deletion. In particular, a patient with a severe bilateral Madelung deformity without short stature showed a homozygous alteration identical to the recently described 47.5 kb PAR1 deletion. Moreover, we identified, for the first time, in three related patients with a severe bilateral Madelung deformity, a smaller deletion than the 47.5 kb PAR1 deletion encompassing the same enhancer region (ECR1/CNE7).
Data reported in this study provide new information about the spectrum of phenotypic alterations showed by LWD patients with different deletions of the SHOX enhancer region.
Madelung deformity; MLPA; SHOX; Short stature
Variants in the emerin gene (EMD) were implicated in X-linked recessive Emery-Dreifuss muscular dystrophy (EDMD), characterized by early-onset contractures of tendons, progressive muscular weakness and cardiomyopathy. To date, 223 mutations have been reported in EMD gene and the majority of them caused a predominant skeletal muscular phenotype. In this study, we identified a novel deletion mutation in EMD exon 1, which results in almost a complete loss of emerin protein in a large Chinese family. However, the patients suffered severe dilated cardiomyopathy (DCM) but very mild skeletal muscle disorder.
Whole exome sequencing (WES) and linkage analysis were performed to identify the underlying mutation in a Chinese DCM family spanning five generations. A missense variation in the GPR50 gene was found co-segregated with the disease phenotype, whereas no functional alteration was detected in the variant GPR50 protein. When analyzing the failure sequences in the exome sequencing data, a novel deletion mutation (c.26_39delATACCGAGCTGACC) in EMD exon 1, was identified in this family. Different from the typical clinical features caused by most reported EMD mutations, patients in our study presented very mild skeletal muscle degeneration that had not been diagnosed until the mutation was found.
We described a family with rare clinical presentations caused by a novel EMD deletion mutation. Our findings broaden the heterogeneous spectrum of phenotypes attributed to EMD mutations and provide new insight to explain the genotype-phenotype correlations between EMD mutations and EDMD symptoms.
Dilated cardiomyopathy; Emery-Dreifuss muscular dystrophy; EMD gene; Novel mutation; Whole exome sequencing
Carnitine is a key molecule in energy metabolism that helps transport activated fatty acids into the mitochondria. Its homeostasis is achieved through oral intake, renal reabsorption and de novo biosynthesis. Unlike dietary intake and renal reabsorption, the importance of de novo biosynthesis pathway in carnitine homeostasis remains unclear, due to lack of animal models and description of a single patient defective in this pathway.
We identified by array comparative genomic hybridization a 42 months-old girl homozygote for a 221 Kb interstitial deletions at 11p14.2, that overlaps the genes encoding Fibin and butyrobetaine-gamma 2-oxoglutarate dioxygenase 1 (BBOX1), an enzyme essential for the biosynthesis of carnitine de novo. She presented microcephaly, speech delay, growth retardation and minor facial anomalies. The levels of almost all evaluated metabolites were normal. Her serum level of free carnitine was at the lower limit of the reference range, while her acylcarnitine to free carnitine ratio was normal.
We present an individual with a completely defective carnitine de novo biosynthesis. This condition results in mildly decreased free carnitine level, but not in clinical manifestations characteristic of carnitine deficiency disorders, suggesting that dietary carnitine intake and renal reabsorption are sufficient to carnitine homeostasis. Our results also demonstrate that haploinsufficiency of BBOX1 and/or Fibin is not associated with Primrose syndrome as previously suggested.
Carnitine; BBOX1; Fibin; CNV; Primrose syndrome
Terminal deletions of chromosome 4q are associated with a broad spectrum of phenotypes including cardiac, craniofacial, digital, and cognitive impairment. The rarity of this syndrome renders genotype-phenotype correlation difficult, which is further complicated by the widely different phenotypes observed in patients sharing similar deletion intervals.
Herein, we describe a boy with congenital hearing impairment and a variety of moderate syndromic features that prompted SNP array analysis disclosing a heterozygous 6.9 Mb deletion in the 4q35.1q35.2 region, which emerged de novo in the maternal germ line.
In addition to the index patient, we review 35 cases from the literature and DECIPHER database to attempt genotype-phenotype correlations for a syndrome with great phenotypic variability. We delineate intervals with recurrent phenotypic overlap, particularly for cleft palate, congenital heart defect, intellectual disability, and autism spectrum disorder. Broad phenotypic presentation of the terminal 4q deletion syndrome is consistent with incomplete penetrance of the individual symptoms.
Genotype-phenotype association; Copy number variation; Parent-of-origin; SNP array; Terminal 4q deletion syndrome
Telomeres are repeated sequences (the hexanucleotide TTAGGG in vertebrates) located at chromosome ends of eukaryotes, protecting DNA from end joining or degradation. Telomeres become shorter with each cell cycle, but telomerase, a ribonucleoprotein complex, alleviates this attrition. The telomerase RNA component (TERC) is an essential element of telomerase, serving as a template for telomere elongation. The H/ACA domain of TERC is indispensable for telomere biogenesis. Mutations in the telomerase components allow accelerated telomere loss, resulting in various disease manifestations, including bone marrow failure. To date, this is the first detailed report of an H-box mutation in TERC that is related to human disease.
A 26-year-old man with myelodysplastic syndrome (MDS) had very short telomeres. Sequencing identified a single heterozygous mutation in the H box of the patient’s TERC gene. The same mutation was also present in his father and his son, demonstrating that it was germline in origin. The telomere length in the father’s blood was shorter compared to age-matched healthy controls, while it was normal in the son and also in the sperm cells of the patient. In vitro experiments suggested that the mutation was responsible for the telomere shortening in the patient’s leukocytes and contributed to the pathogenesis of bone marrow failure in our patient.
We analyzed a mutation (A377G) in the H box of TERC in a young MDS patient who had significantly short-for-age telomeres. As telomeres protect chromosomes from instability, it is highly plausible that this genetic lesion was responsible for the patient’s hematological manifestations, including marrow failure and aneuploidy in the hematopoietic stem cell compartment.
Myelodysplastic syndrome (MDS); Telomerase RNA component (TERC); H/ACA box; Southern blotting; Single Telomere Elongation Length Analysis (STELA); RNA fluorescence in situ hybridization (RNA FISH)
Shwachman–Diamond syndrome (SDS) is an autosomal recessive ribosomopathy caused mainly by compound heterozygous mutations in SBDS. Structural variation (SV) involving the SBDS locus has been rarely reported in association with the disease. We aimed to determine whether an SV contributed to the pathogenesis of a case lacking biallelic SBDS point mutations.
Whole exome sequencing was performed in a patient with SDS lacking biallelic SBDS point mutations. Array comparative genomic hybridization and Southern blotting were used to seek SVs across the SBDS locus. Locus-specific polymerase chain reaction (PCR) encompassing flanking intronic sequence was also performed to investigate mutation within the locus. RNA expression and Western blotting were performed to analyze allele and protein expression. We found the child harbored a single missense mutation in SBDS (c.98A > C; p.K33T), inherited from the mother, and an SV in the SBDS locus, inherited from the father. The missense allele and SV segregated in accordance with Mendelian expectations for autosomal recessive SDS. Complementary DNA and western blotting analysis and locus specific PCR support the contention that the SV perturbed SBDS protein expression in the father and child.
Our findings implicate genomic rearrangements in the pathogenesis of some cases of SDS and support patients lacking biallelic SBDS point mutations be tested for SV within the SBDS locus.
Shwachman-Diamond syndrome; SBDS; Structural variation; Genomic rearrangement; Non-allelic homologous recombination; Low copy repeat; Whole exome sequencing; Copy number variation; Recessive disease
Poland Syndrome (PS) is a rare disorder characterized by hypoplasia/aplasia of the pectoralis major muscle, variably associated with thoracic and upper limb anomalies. Familial recurrence has been reported indicating that PS could have a genetic basis, though the genetic mechanisms underlying PS development are still unknown.
Here we describe a couple of monozygotic (MZ) twin girls, both presenting with Poland Syndrome. They carry a de novo heterozygous 126 Kbp deletion at chromosome 11q12.3 involving 5 genes, four of which, namely HRASLS5, RARRES3, HRASLS2, and PLA2G16, encode proteins that regulate cellular growth, differentiation, and apoptosis, mainly through Ras-mediated signaling pathways.
Phenotype concordance between the monozygotic twin probands provides evidence supporting the genetic control of PS. As genes controlling cell growth and differentiation may be related to morphological defects originating during development, we postulate that the observed chromosome deletion could be causative of the phenotype observed in the twin girls and the deleted genes could play a role in PS development.
Chromosome 11q deletion; Congenital abnormalities; Monozygotic twins; Poland syndrome; CNV; HRASLS5; HRASLS2; RARRES3; PLA2G16
Association of melanoma, neural system tumors and germ line mutations at the 9p21 region in the CDKN2A, CDKN2B and CDKN2BAS genes has been reported in a small number of families worldwide and described as a discrete syndrome in melanoma families registered as a rare disease, the melanoma–astrocytoma syndrome.
We here studied two young patients developing melanoma after radiotherapy for astrocytoma, both reporting lack of family history for melanoma or neural system tumors at genetic counselling. Patient A is a girl treated for anaplastic astrocytoma at 10 years and for multiple melanomas on the scalp associated to dysplastic nevi two years later. Her monozygotic twin sister carried dysplastic nevi and a slow growing, untreated cerebral lesion. Direct sequencing analysis showed no alterations in melanoma susceptibility genes including CDKN2A, CDK4, MC1R and MITF or in TP53. By microsatellite analysis, multiplex ligation-dependent probe amplification, and array comparative genomic hybridization a deletion including the CDKN2A, CDKN2B and CDKN2BAS gene cluster was detected in both twin sisters, encompassing a large region at 9p21.3 and occurring de novo after the loss of one paternal allele.
Patient B is a boy of 7 years when treated for astrocytoma then developing melanoma associated to congenital nevi on the head 10 years later: sequencing and multiplex ligation-dependent probe amplification revealed a normal profile of the CDKN2A/CDKN2B/CDKN2BAS region. Array comparative genomic hybridization confirmed the absence of deletions at 9p21.3 and failed to reveal known pathogenic copy number variations.
By comparison with the other germ line deletions at the CDKN2A, CDKN2B and CDKN2BAS gene cluster reported in melanoma susceptible families, the deletion detected in the two sisters is peculiar for its de novo origin and for its extension, as it represents the largest constitutive deletion at 9p21.3 region identified so far.
In addition, the two studied cases add to other evidence indicating association of melanoma with exposure to ionizing radiation and with second neoplasm after childhood cancer. Melanoma should be considered in the monitoring of pigmented lesions in young cancer patients.
Melanoma-astrocytoma syndrome; 9p21.3 deletion; CDKN2A; CDKN2BAS; MLPA; Oligo array-CGH
SHORT syndrome is a rare autosomal dominant condition whose name is the acronym of short stature, hyperextensibility of joints, ocular depression, Rieger anomaly and teething delay (MIM 269880). Additionally, the patients usually present a low birth weight and height, lipodystrophy, delayed bone age, hernias, low body mass index and a progeroid appearance.
In this study, we used whole-exome sequencing approaches in two patients with clinical features of SHORT syndrome. We report the finding of a novel mutation in PIK3R1 (c.1929_1933delTGGCA; p.Asp643Aspfs*8), as well as a recurrent mutation c.1945C > T (p.Arg649Trp) in this gene.
We found a novel frameshift mutation in PIK3R1 (c.1929_1933delTGGCA; p.Asp643Aspfs*8) which consists of a deletion right before the site of substrate recognition. As a consequence, the protein lacks the position that interacts with the phosphotyrosine residue of the substrate, resulting in the development of SHORT syndrome.
Aging; Diabetes; Insulin; Kinase; Lipodystrophy; Progeria
Trichorhinophalangeal syndrome (TRPS) is a rare autosomal dominant genetic disorder characterised by distinctive craniofacial and skeletal abnormalities. TRPS is generally associated with mutations in the TRPS1 gene at 8q23.3 or microdeletions of the 8q23.3-q24.11 region. However, three deletions affecting the same chromosome region and a familial translocation t(8;13) co-segregating with TRPS, which do not encompass or disrupt the TRPS1 gene, have been reported. A deregulated expression of TRPS1 has been hypothesised as cause of the TRPS phenotype of these patients.
We report the clinical and molecular characterisation of a 57-year-old Caucasian woman carrying the t(2;8)(p16.1;q23.3) de novo balanced translocation. The proband presented with peculiar clinical features (severe craniofacial dysmorphism, alopecia universalis, severe scoliosis, mitral valve prolapse, mild mental impairment and normal growth parameters) that partially overlap with TRPS I. Mutational and array CGH analyses ruled out any genetic defect affecting TRPS1 or genomic alteration at the translocation breakpoint or elsewhere in the genome. Breakpoint mapping excluded disruption of TRPS1, and revealed that the chromosome 8q23.3 breakpoint was located within the IVS10 of the long intergenic non-coding RNA LINC00536, at approximately 300 kb from the TRPS1 5’ end. Conversely, the 2p16.1 breakpoint mapped within a LINE sequence, in a region that lacks transcriptional regulatory elements. As a result of the translocation, nucleotide base pair additions and deletions were detected at both breakpoint junction fragments, and an evolutionarily conserved VISTA enhancer element from 2p16.1 was relocated at approximately 325 kb from the TRPS1 promoter.
We suggest that the disruption of the genomic architecture of cis regulatory elements downstream the TRPS1 5′ region, combined with the translocation of a novel enhancer element nearby TRPS1, might be the pathogenetic mechanism underpinning the proband’s phenotype. The clinical and genetic characterisation of the present subject allowed us to make a genetic diagnosis in the context of a known syndrome, contributing to a better comprehension of the complex transcriptional regulation of TRPS1 and TRPS ethiopathogenesis.
Reciprocal translocation; Conserved enhancer element; TRPS; TRPS1
Wiedemann-Steiner Syndrome (WSS) is characterized by short stature, a variety of dysmorphic facial and skeletal features, characteristic hypertrichosis cubiti (excessive hair on the elbows), mild-to-moderate developmental delay and intellectual disability. [MIM#: 605130]. Here we report two unrelated children for whom clinical exome sequencing of parent-proband trios was performed at UCLA, resulting in a molecular diagnosis of WSS and atypical clinical presentation.
For patient 1, clinical features at 9 years of age included developmental delay, craniofacial abnormalities, and multiple minor anomalies. Patient 2 presented at 1 year of age with developmental delay, microphthalmia, partial 3–4 left hand syndactyly, and craniofacial abnormalities. A de novo missense c.4342T>C variant and a de novo splice site c.4086+G>A variant were identified in the KMT2A gene in patients 1 and 2, respectively.
Based on the clinical and molecular findings, both patients appear to have novel presentations of WSS. As the hallmark hypertrichosis cubiti was not initially appreciated in either case, this syndrome was not suspected during the clinical evaluation. This report expands the phenotypic spectrum of the clinical phenotypes and KMT2A variants associated with WSS.
Wiedemann-Steiner syndrome; Clinical exome sequencing; KMT2A; Intellectual disability; Developmental delay
Long-QT syndrome (LQTS) causes a prolongation of the QT-interval in the ECG leading to life threatening tachyarrhythmia and ventricular fibrillation. One atypical form of LQTS, Timothy syndrome (TS), is associated with syndactyly, immune deficiency, cognitive and neurological abnormalities as well as distinct cranio-facial abnormalities.
On a family with both children diagnosed with clinical LQTS, we performed whole exome sequencing to comprehensively screen for causative mutations after a targeted candidate gene panel screen for Long-QT syndrome target genes failed to identify any underlying genetic defect. Using exome sequencing, we identified in both affected children, a p.402G > S mutation in exon 8 of the CACNA1C gene, a voltage-dependent Ca2+ channel. The mutation was inherited from their father, a mosaic mutation carrier. Based on this molecular finding and further more careful clinical examination, we refined the diagnosis to be Timothy syndrome (TS2) and thereby were able to present new therapeutic approaches.
Our study highlights the difficulties in accurate diagnosis of patients with rare diseases, especially those with atypical clinical manifestation. Such challenge could be addressed with the help of comprehensive and unbiased mutation screening, such as exome sequencing.
Timothy syndrome; Exome sequencing; Mosaic mutation; LQTS
Diagnosis within RASopathies still represents a challenge. Nevertheless, many efforts have been made by clinicians to identify specific clinical features which might help in differentiating one disorder from another. Here, we describe a child initially diagnosed with Neurofibromatosis-Noonan syndrome. The follow-up of the proband, the clinical evaluation of his father together with a gene-by-gene testing approach led us to the proper diagnosis.
We report a 8-year-old male with multiple café-au-lait macules, several lentigines and dysmorphic features that suggest Noonan syndrome initially diagnosed with Neurofibromatosis-Noonan syndrome. However, after a few years of clinical and ophthalmological follow-up, the absence of typical features of Neurofibromatosis type 1 and the lack of NF1 mutation led us to reconsider the original diagnosis. A new examination of the patient and his similarly affected father, who was initially referred as healthy, led us to suspect LEOPARD syndrome, The diagnosis was then confirmed by the occurrence in both patients of a heterozygous mutation c.1403 C > T, p.(Thr468Met), of PTPN11. Subsequently, the proband was also found to have type-1 Arnold-Chiari malformation in association with syringomyelia.
Our experience suggests that differential clinical diagnosis among RASopathies remains ambiguous and raises doubts on the current diagnostic clinical criteria. In some cases, genetic tests represent the only conclusive proof for a correct diagnosis and, consequently, for establishing individual prognosis and providing adequate follow-up. Thus, molecular testing represents an essential tool in differential diagnosis of RASophaties. This view is further strengthened by the increasing accessibility of new sequencing techniques.
Finally, to our knowledge, the described case represents the third report of the occurrence of Arnold Chiari malformation and the second description of syringomyelia with LEOPARD syndrome.
LEOPARD syndrome; Neurofibromatosis type 1; RASopathy; PTPN11
The hereditary spastic paraplegias (HSPs) are pleiomorphic disorders of motor pathway and a large number of affected genes have been discovered. Yet, mutations in SPG4/SPAST represent the most frequent molecular etiology in autosomal dominant (AD) patients and sporadic cases. We describe a large, AD-HSP Sardinian family where 5 out of several living members harbored a novel deletion affecting also the 5′UTR of SPAST and resulting in reduced expression of DPY30, the gene located upstream SPAST in a head-to-head manner.
A 54-year-old woman manifested leg stiffness at age 39 and required a cane to walk at age 50. Neurological examination disclosed mild spasticity and weakness in the legs, hyperreflexia in all limbs, and bilateral Babinski sign. She also complained of urinary urgency, but no additional neurological symptoms or signs were detected at examination. The clinical examination of 24 additional relatives disclosed three further affected individuals, two men and one woman. In the four symptomatic patients the initial manifestations were walking abnormalities and leg stiffness with a mean age at onset (SD) of 46.75 (5.44) years (range 39–51). The mean disease duration was 13.2 (13.4) years (range 6–35), and it correlated well with clinical severity (SPRS score) (r = 0.975, p = 0.005). One patient was confined to bed and displayed knee and ankle contractures, another case needed a cane to walk, and two individuals were able to walk without aids. Interestingly, a patient had also had a miscarriage during her first pregnancy.
Gene testing revealed an heterozygous deletion spanning from the 5′-UTR to intron 4 of SPAST in the affected individuals and in one clinically unaffected woman. In three affected patients, the deletion also determined low mRNA levels of SPAST and DPY30, a component of the Set1-like multiprotein histone methyltransferase complex located upstream, head-to-head with SPAST.
Together with data described in a Japanese family, our findings seem to suggest that genes close to spastin might be candidates in modulating the clinical phenotype. This report endorses future research on the role of neighboring genes as potential players in SPG4 disease variability.
SPG4; DPY30; Genetic modifier; Deletion
Glycyl-tRNA synthetase (GARS) is an aminoacyl-tRNA synthetase (ARS) that links the amino acid glycine to its corresponding tRNA prior to protein translation and is one of three bifunctional ARS that are active within both the cytoplasm and mitochondria. Dominant mutations in GARS cause rare forms of Charcot-Marie-Tooth disease and distal spinal muscular atrophy.
We report a 12-year old girl who presented with clinical and biochemical features of a systemic mitochondrial disease including exercise-induced myalgia, non-compaction cardiomyopathy, persistent elevation of blood lactate and alanine and MRI evidence of mild periventricular leukomalacia. Using exome sequencing she was found to harbor compound heterozygous mutations within the glycyl-tRNA synthetase (GARS) gene; c.1904C > T; p.Ser635Leu and c.1787G > A; p.Arg596Gln. Each mutation occurred at a highly conserved site within the anticodon binding domain.
Our findings suggest that recessive mutations in GARS may cause systemic mitochondrial disease. This phenotype is distinct from patients with previously reported dominant mutations in this gene, thereby expanding the spectrum of disease associated with GARS dysregulation.
Glycyl-tRNA synthetase; Amino acyl-tRNA synthetase; Cardiomyopathy; Charcot-Marie-tooth disease
SCN2A is a gene that codes for the alpha subunit of voltage-gated, type II sodium channels, and is highly expressed in the brain. Sodium channel disruptions, such as mutations in SCN2A, may play an important role in psychiatric disorders. Recently, de novo SCN2A mutations in autism spectrum disorder (ASD) have been identified. The current study characterizes a de novo splice site mutation in SCN2A that alters mRNA and protein products.
We describe results from clinical and genetic characterizations of a seven-year-old boy with ASD. Psychiatric interview and gold standard autism diagnostic instruments (ADOS and ADI-R) were used to confirm ASD diagnosis, in addition to performing standardized cognitive and adaptive functioning assessments (Leiter-R and Vineland Adaptive Behavior Scale), and sensory reactivity assessments (Sensory Profile and Sensory Processing Scales). Genetic testing by whole exome sequencing revealed four de novo events, including a splice site mutation c.476 + 1G > A in SCN2A, a missense mutation (c.2263G > A) causing a p.V755I change in the TLE1 gene, and two synonymous mutations (c.2943A > G in the BUB1 gene, and c.1254 T > A in C10orf68 gene). The de novo SCN2A splice site mutation produced a stop codon 10 amino acids downstream, possibly resulting in a truncated protein and/or a nonsense-mediated mRNA decay. The participant met new DSM-5 criteria for ASD, presenting with social and communication impairment, repetitive behaviors, and sensory reactivity issues. The participant’s adaptive and cognitive skills fell in the low range of functioning.
This report indicates that a splice site mutation in SCN2A might be contributing to the risk of ASD. Describing the specific phenotype associated with SCN2A mutations might help to reduce heterogeneity seen in ASD.
DSM-5; autism spectrum disorder; de novo SCN2A splice site mutation
α/β-hydrolase domain-containing protein 5 (ABHD5) plays an important role in the triacylglycerols (TAG) hydrolysis. Indeed, ABHD5 is the co-activator of adipose triglyceride lipase (ATGL), that catalyses the initial step of TAG hydrolysis. Mutations in ABHD5 gene are associated with the onset of Chanarin-Dorfman syndrome (CDS), a rare autosomal recessive lipid storage disorder, characterized by non-bullous congenital ichthyosiform erythroderma (NCIE), hepatomegaly and liver steatosis.
We describe here a 5-years-old Brazilian child who presented with NCIE at birth and diffuse micro and macro-vesicular steatosis on liver biopsy since she was 2 years old. Molecular analysis of coding sequence and putative 5′ regulatory region of ABHD5 gene was performed. A homozygous novel deletion, affecting the promoter region and the exon 1, was identified, confirming the suspected diagnosis of CDS for this patient. RT-PCR analysis showed that the genomic rearrangement completely abolished the ABHD5 gene expression in the patient, while only a partial loss of expression was detected in her parents. This is the first report describing the identification of a large deletion encompassing the promoter region of ABHD5 gene. The total loss of ABHD5 expression may explain the early onset of CDS and the severe liver involvement. After molecular diagnosis, the patient started a special diet, poor in fatty acids with medium chain triglycerides (MCT), and showed hepatic and dermatologic improvement in spite of severe molecular defect.
This case report extends the spectrum of disease-causing ABHD5 mutations in CDS providing evidence for a novel pathogenic mechanism for this rare disorder. Moreover, our preliminary data show that early diagnosis and prompt treatment of neutral lipid accumulation might be useful for CD patients.
Chanarin-Dorfman syndrome; ABHD5; Lipid disorder; Liver involvement; Ichthyosis
D-bifunctional protein deficiency, caused by recessive mutations in HSD17B4, is a severe, infantile-onset disorder of peroxisomal fatty acid oxidation. Few affected patients survive past two years of age. Compound heterozygous mutations in HSD17B4 have also been reported in two sisters diagnosed with Perrault syndrome (MIM # 233400), who presented in adolescence with ovarian dysgenesis, hearing loss, and ataxia.
An adult male presented with cerebellar ataxia, peripheral neuropathy, hearing loss, and azoospermia. The clinical presentation, in combination with biochemical findings in serum, urine, and muscle biopsy, suggested a mitochondrial disorder. Commercial genetic testing of 18 ataxia and mitochondrial disease genes was negative. Targeted exome sequencing followed by analysis of single nucleotide variants and small insertions/deletions failed to reveal a genetic basis of disease. Application of a computational algorithm to infer copy number variants (CNVs) from exome data revealed a heterozygous 12 kb deletion of exons 10–13 of HSD17B4 that was compounded with a rare missense variant (p.A196V) at a highly conserved residue. Retrospective review of patient records revealed mildly elevated ratios of pristanic:phytanic acid and arachidonic:docosahexaenoic acid, consistent with dysfunctional peroxisomal fatty acid oxidation.
Our case expands the phenotypic spectrum of HSD17B4-deficiency, representing the first male case reported with infertility. Furthermore, it points to crosstalk between mitochondria and peroxisomes in HSD17B4-deficiency and Perrault syndrome.
HSD17B4; DBP; D-bifunctional protein deficiency; Perrault syndrome; Next-generation sequencing; Exome sequencing; Copy number variants; CNV; Mitochondria; Mitochondrial disorders; Mitochondrial disease; Mendelian disorders; Human genetics; Ataxia; Multi-system disorders; Peroxisomal defects
Wilson’s disease (WD), a rare cause of neuropsychiatric deterioration, is associated with mutations in the ATP7B gene. Prion diseases are also rare causes of neuropsychiatric deterioration that can occur sporadically without an identifiable cause, or can be attributed to mutations in the PRNP gene.
Here we describe a biological “experiment of nature” in which a patient presented with severe neuropsychiatric decline and strong biochemical evidence of WD. Genetic analysis revealed that he was a compound heterozygote for two ATP7B sequence variants (c.2165dupT, p.Arg723Glufs*32; and c.4039G > A, p.Gly1347Ser), the first having been reported once previously, and the second being novel. In addition, the patient was heterozygous for a PRNP variant, c.160G > A, p.Gly54Ser, that has been reported in a neuropsychiatric patient only once previously in association with a similarly severe clinical course of neuropsychiatric disease and early age of onset, but no accompanying information on ATP7B genotype. Of particular interest was the observation that the patient’s older sister, who carried the same ATP7B genotype and laboratory evidence for biochemical WD but was clinically asymptomatic, lacked the PRNP variant allele.
We propose that synergism may occur between at least some allelic variants of ATP7B and PRNP, possibly exerted through effects on cellular copper metabolism.
Wilson’s disease; Prion disease; Copper; ATP7B; PRNP; Prion protein; PrP; Synergistic mutations; Movement disorder
Rearrangements involving chromosome 5p often result in two syndromes, Cri-du-chat (CdC) and Trisomy 5p, caused by a deletion and duplication, respectively. The 5p15.2 has been defined as a critical region for CdC syndrome; however, genotype-phenotype studies allowed isolation of particular characteristics such as speech delay, cat-like cry and mental retardation, caused by distinct deletions of 5p. A varied clinical outcome was also observed in patients with Trisomy 5p. Duplications of 5p10-5p13.1 manifest themselves in a more severe phenotype, while trisomy of regions distal to 5p13 mainly causes mild and indistinct features. Combinations of a terminal deletion and inverted duplication of 5p are infrequent in literature. Consequences of these chromosomal rearrangements differ, depending on size of deletion and duplication in particular cases, although authors mainly describe the deletion as the cause of the observed clinical picture.
Here we present a 5-month-old Slovenian girl, with de novo terminal deletion and inverted duplication of chromosome 5p. Our patient presents features of both CdC and Trisomy 5. The most prominent features observed in our patient are a cat-like cry and severe malformations of the right ear.
The cat-like cry, characteristic of CdC syndrome, is noted in our patient despite the fact that the deletion is not fully consistent with previously defined cat-like cry critical region in this syndrome. Features like dolichocephaly, macrocephaly and ear malformations, associated with duplication of the critical region of Trisomy 5p, are also present, although this region has not been rearranged in our case. Therefore, the true meaning of the described chromosomal rearrangements is discussed.
Deletion with inverted duplication of 5p; Cri-du-chat syndrome; Trisomy 5p; Cat-like cry; Ear agenesis
Deletion of the subtelomeric region of 1p36 is one of the most common subtelomeric deletion syndromes. In monosomy 1p36, the presence of obesity is poorly defined, and glucose metabolism deficiency is rarely reported. However, the presence of a typical Prader-Willi-like phenotype in patients with monosomy 1p36 is controversial.
In this report, we describe two female patients, one who is 6 years 2 months of age and another who is 10 years 1 month of age, both referred to our hospital for obesity and a Prader-Willi-like phenotype. These patients presented with severe obesity (body mass index [BMI] was 26.4 and 27.7, respectively), hyperphagia and developmental delay. Analysis of basal hormone levels showed normal thyroid function and adrenal function but considerable basal hyperinsulinism (the insulin levels were 54.5 and 49.2 μU/ml, respectively). In patient 1, glycaemia was 75 mg/dl (HOMA-R 10.09), and the HbA1c level was 6.1%; in patient 2, glycaemia was 122 mg/dl, and the HbA1c level was 6.6% (HOMA-R 14.82). An oral glucose tolerance test demonstrated impaired glucose tolerance and diabetes mellitus with marked insulin resistance (the peak insulin level for each patient was 197 and 279 μU/mL, respectively, while the 120’ insulin level of each patient was 167 and 234 μU/mL, respectively).
some patients with monosomy 1p36 may show Prader-Willi-like physical and physiologic characteristics such as obesity and hyperinsulinism with impaired glucose metabolism, which can cause type II diabetes mellitus. Further studies are necessary to evaluate these findings.
Monosomy 1p36; Deletion 1p36; Developmental delay; Mental retardation; Seizures; Obesity; Hyperinsulinism; Impaired glucose tolerance; Hyperphagia; Prader-Willi-like phenotype
Kabuki syndrome (KS) is a rare, multiple congenital anomalies/intellectual disability syndrome caused by mutations of MLL2 gene, which codifies for a histone methyltrasferase that regulates the embryogenesis and the tissue development. Left-bronchial isomerism is a rare congenital abnormality that can be defined as the absence of the normal lateralizing features which distinguish right and left-sides in the lungs. To date, this is the first report of left-bronchial isomerism in association with KS.
A one-month-old Caucasian male patient underwent our attention for microcephaly, dysmorphic features (long palpebral fissures, eyebrows with sparse lateral third, everted lower eyelids, blue sclerae, large dysplastic ears, lower lip pits), persistent fetal fingertip pads, short stature, heart defects (interventricular defect and aortic coarctation), unilateral cryptorchidism, hypotonia and delay in gross motor skills. These features suggested a diagnosis of KS and a molecular analysis confirmed a novel frame-shift mutation in the exon 11 of MLL2 gene. Subsequently, given recurrent respiratory infections with a normal immunological status, he underwent a chest CT scan that showed a left bronchial isomerism.
We report a patient affected by KS, with a novel MLL2 mutation and an atypical phenotype characterized by left-side bronchial isomerism. Interestingly, genes involved in the heterotaxia/isomerism such as ROCK2 and SHROOM3 are known to interact with MLL2 gene. In order to achieve a correct diagnosis and an appropriate therapy, the presence of pulmonary anatomical variations should be investigated in KS patients with respiratory signs not associated to immunological deficiency. Finally, our findings support the hypothesis that the mutations leading to a complete loss of function of MLL2 gene is often associated with complex visceral malformations.
Kabuki syndrome; Isomerism; Respiratory distress