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1.  Limbal Stem Cell Transplantation 
Executive Summary
The objective of this analysis is to systematically review limbal stem cell transplantation (LSCT) for the treatment of patients with limbal stem cell deficiency (LSCD). This evidence-based analysis reviews LSCT as a primary treatment for nonpterygium LSCD conditions, and LSCT as an adjuvant therapy to excision for the treatment of pterygium.
Clinical Need: Condition and Target Population
The outer surface of the eye is covered by 2 distinct cell layers: the corneal epithelial layer that overlies the cornea, and the conjunctival epithelial layer that overlies the sclera. These cell types are separated by a transitional zone known as the limbus. The corneal epithelial cells are renewed every 3 to 10 days by a population of stem cells located in the limbus.
Nonpterygium Limbal Stem Cell Deficiency
When the limbal stem cells are depleted or destroyed, LSCD develops. In LSCD, the conjunctival epithelium migrates onto the cornea (a process called conjunctivalization), resulting in a thickened, irregular, unstable corneal surface that is prone to defects, ulceration, corneal scarring, vascularization, and opacity. Patients experience symptoms including severe irritation, discomfort, photophobia, tearing, blepharospasm, chronic inflammation and redness, and severely decreased vision.
Depending on the degree of limbal stem cell loss, LSCD may be total (diffuse) or partial (local). In total LSCD, the limbal stem cell population is completed destroyed and conjunctival epithelium covers the entire cornea. In partial LSCD, some areas of the limbus are unharmed, and the corresponding areas on the cornea maintain phenotypically normal corneal epithelium.
Confirmation of the presence of conjunctivalization is necessary for LSCD diagnosis as the other characteristics and symptoms are nonspecific and indicate a variety of diseases. The definitive test for LSCD is impression cytology, which detects the presence of conjunctival epithelium and its goblet cells on the cornea. However, in the opinion of a corneal expert, diagnosis is often based on clinical assessment, and in the expert’s opinion, it is unclear whether impression cytology is more accurate and reliable than clinical assessment, especially for patients with severe LSCD.
The incidence of LSCD is not well understood. A variety of underlying disorders are associated with LSCD including chemical or thermal injuries, ultraviolet and ionizing radiation, Stevens-Johnson syndrome, multiple surgeries or cryotherapies, contact lens wear, extensive microbial infection, advanced ocular cicatricial pemphigoid, and aniridia. In addition, some LSCD cases are idiopathic. These conditions are uncommon (e.g., the prevalence of aniridia ranges from 1 in 40,000 to 1 in 100,000 people).
Pterygium is a wing-shaped fibrovascular tissue growth from the conjunctiva onto the cornea. Pterygium is the result of partial LSCD caused by localized ultraviolet damage to limbal stem cells. As the pterygium invades the cornea, it may cause irregular astigmatism, loss of visual acuity, chronic irritation, recurrent inflammation, double vision, and impaired ocular motility.
Pterygium occurs worldwide. Incidence and prevalence rates are highest in the “pterygium belt,” which ranges from 30 degrees north to 30 degrees south of the equator, and lower prevalence rates are found at latitudes greater than 40 degrees. The prevalence of pterygium for Caucasians residing in urban, temperate climates is estimated at 1.2%.
Existing Treatments Other Than Technology Being Reviewed
Nonpterygium Limbal Stem Cell Deficiency
In total LSCD, a patient’s limbal stem cells are completely depleted, so any successful treatment must include new stem cells. Autologous oral mucosal epithelium transplantation has been proposed as an alternative to LSCT. However, this procedure is investigational, and there is very limited level 4c evidence1 to support this technique (fewer than 20 eyes examined in 4 case series and 1 case report).
For patients with partial LSCD, treatment may not be necessary if their visual axis is not affected. However, if the visual axis is conjunctivalized, several disease management options exist including repeated mechanical debridement of the abnormal epithelium; intensive, nonpreserved lubrication; bandage contact lenses; autologous serum eye drops; other investigational medical treatments; and transplantation of an amniotic membrane inlay. However, these are all disease management treatments; LSCT is the only curative option.
The primary treatment for pterygium is surgical excision. However, recurrence is a common problem after excision using the bare sclera technique: reported recurrence rates range from 24% to 89%. Thus, a variety of adjuvant therapies have been used to reduce the risk of pterygium recurrence including LSCT, amniotic membrane transplantation (AMT), conjunctival autologous (CAU) transplantation, and mitomycin C (MMC, an antimetabolite drug).
New Technology Being Reviewed
To successfully treat LSCD, the limbal stem cell population must be repopulated. To achieve this, 4 LSCT procedures have been developed: conjunctival-limbal autologous (CLAU) transplantation; living-related conjunctival-limbal allogeneic (lr-CLAL) transplantation; keratolimbal allogeneic (KLAL) transplantation; and ex vivo expansion of limbal stem cells transplantation. Since the ex vivo expansion of limbal stem cells transplantation procedure is considered experimental, it has been excluded from the systematic review. These procedures vary by the source of donor cells and the amount of limbal tissue used. For CLAU transplants, limbal stem cells are obtained from the patient’s healthy eye. For lr-CLAL and KLAL transplants, stem cells are obtained from living-related and cadaveric donor eyes, respectively.
In CLAU and lr-CLAL transplants, 2 to 4 limbal grafts are removed from the superior and inferior limbus of the donor eye. In KLAL transplants, the entire limbus from the donor eye is used.
The recipient eye is prepared by removing the abnormal conjunctival and scar tissue. An incision is made into the conjunctival tissue into which the graft is placed, and the graft is then secured to the neighbouring limbal and scleral tissue with sutures. Some LSCT protocols include concurrent transplantation of an amniotic membrane onto the cornea.
Regulatory Status
Health Canada does not require premarket licensure for stem cells. However, they are subject to Health Canada’s clinical trial regulations until the procedure is considered accepted transplantation practice, at which time it will be covered by the Safety of Human Cells, Tissues and Organs for Transplantation Regulations (CTO Regulations).
Review Strategy
The Medical Advisory Secretariat systematically reviewed the literature to assess the effectiveness and safety of LSCT for the treatment of patients with nonpterygium LSCD and pterygium. A comprehensive search method was used to retrieve English-language journal articles from selected databases.
The GRADE approach was used to systematically and explicitly evaluate the quality of evidence and strength of recommendations.
Summary of Findings
Nonpterygium Limbal Stem Cell Deficiency
The search identified 873 citations published between January 1, 2000, and March 31, 2008. Nine studies met the inclusion criteria, and 1 additional citation was identified through a bibliography review. The review included 10 case series (3 prospective and 7 retrospective).
Patients who received autologous transplants (i.e., CLAU) achieved significantly better long-term corneal surface results compared with patients who received allogeneic transplants (lr-CLAL, P< .001; KLAL, P< .001). There was no significant difference in corneal surface outcomes between the allogeneic transplant options, lr-CLAL and KLAL (P = .328). However, human leukocyte antigen matching and systemic immunosuppression may improve the outcome of lr-CLAL compared with KLAL. Regardless of graft type, patients with Stevens-Johnson syndrome had poorer long-term corneal surface outcomes.
Concurrent AMT was associated with poorer long-term corneal surface improvements. When the effect of the AMT was removed, the difference between autologous and allogeneic transplants was much smaller.
Patients who received CLAU transplants had a significantly higher rate of visual acuity improvements compared with those who received lr-CLAL transplants (P = .002). However, to achieve adequate improvements in vision, patients with deep corneal scarring will require a corneal transplant several months after the LSCT.
No donor eye complications were observed.
Epithelial rejection and microbial keratitis were the most common long-term complications associated with LSCT (complications occurred in 6%–15% of transplantations). These complications can result in graft failure, so patients should be monitored regularly following LSCT.
The search yielded 152 citations published between January 1, 2000 and May 16, 2008. Six randomized controlled trials (RCTs) that evaluated LSCT as an adjuvant therapy for the treatment of pterygium met the inclusion criteria and were included in the review.
Limbal stem cell transplantation was compared with CAU, AMT, and MMC. The results showed that CLAU significantly reduced the risk of pterygium recurrence compared with CAU (relative risk [RR], 0.09; 95% confidence interval [CI], 0.01–0.69; P = .02). CLAU reduced the risk of pterygium recurrence for primary pterygium compared with MMC, but this comparison did not reach statistical significance (RR, 0.48; 95% CI, 0.21–1.10; P = .08). Both AMT and CLAU had similar low rates of recurrence (2 recurrences in 43 patients and 4 in 46, respectively), and the RR was not significant (RR, 1.88; 95% CI, 0.37–9.5; P = .45). Since sample sizes in the included studies were small, failure to detect a significant difference between LSCT and AMT or MMC could be the result of type II error. Limbal stem cell transplantation as an adjuvant to excision is a relatively safe procedure as long-term complications were rare (< 2%).
GRADE Quality of Evidence
Nonpterygium Limbal Stem Cell Deficiency
The evidence for the analyses related to nonpterygium LSCD was based on 3 prospective and 7 retrospective case series. Thus, the GRADE quality of evidence is very low, and any estimate of effect is very uncertain.
The analyses examining LSCT as an adjuvant treatment option for pterygium were based on 6 RCTs. The quality of evidence for the overall body of evidence for each treatment option comparison was assessed using the GRADE approach. In each of the comparisons, the quality of evidence was downgraded due to serious or very serious limitations in study quality (individual study quality was assessed using the Jadad scale, and an assessment of allocation concealment and the degree of loss to follow-up), which resulted in low- to moderate-quality GRADE evidence ratings (low-quality evidence for the CLAU and AMT and CLAU and MMC comparisons, and moderate-quality evidence for the CLAU and CAU comparison).
Ontario Health System Impact Analysis
Nonpterygium Limbal Stem Cell Deficiency
Since 1999, Ontario’s out-of-country (OOC) program has approved and reimbursed 8 patients for LSCTs and 1 patient for LSCT consultations. Similarly, most Canadian provinces have covered OOC or out-of-province LSCTs. Several corneal experts in Ontario have the expertise to perform LSCTs.
As there are no standard guidelines for LSCT, patients who receive transplants OOC may not receive care aligned with the best evidence. To date, many of the patients from Ontario who received OOC LSCTs received concurrent AMTs, and the evidence from this analysis questions the use of this procedure. In addition, 1 patient received a cultured LSCT, a procedure that is considered investigational. Many patients with LSCD have bilateral disease and therefore require allogeneic transplants. These patients will require systemic and topical immunosuppression for several years after the transplant, perhaps indefinitely. Thus, systemic side effects associated with immunosuppression are a potential concern, and patients must be monitored regularly.
Amniotic membrane transplantation is a common addition to many ocular surface reconstruction procedures, including LSCT. Amniotic membranes are recovered from human placentas from planned, uneventful caesarean sections. Before use, serological screening of the donor’s blood should be conducted. However, there is still a theoretical risk of disease transmission associated with this procedure.
Financial Impact
For the patients who were reimbursed for OOC LSCTs, the average cost of LSCT per eye was $18,735.20 Cdn (range, $8,219.54–$33,933.32). However, the actual cost per patient is much higher as these costs do not include consultations and follow-up visits, multiple LSCTs, and any additional procedures (e.g., corneal transplants) received during the course of treatment OOC. When these additional costs were considered, the average cost per patient was $57,583 Cdn (range, $8,219.54–$130,628.20).
The estimated average total cost per patient for performing LSCT in Ontario is $2,291.48 Cdn (range, $951.48–$4,538.48) including hospital and physician fees. This cost is based on the assumption that LSCT is technically similar to a corneal transplant, an assumption which needs to be verified. The cost does not include corneal transplantations, which some proportion of patients receiving a LSCT will require within several months of the limbal transplant.
Pterygium recurrence rates after surgical excision are high, ranging from 24% to 89%. However, according to clinical experts, the rate of recurrence is low in Ontario. While there is evidence that the prevalence of pterygium is higher in the “pterygium belt,” there was no evidence to suggest different recurrence rates or disease severity by location or climate.
Nonpterygium Limbal Stem Cell Deficiency
Successful LSCTs result in corneal re-epithelialization and improved vision in patients with LSCD. However, patients who received concurrent AMT had poorer long-term corneal surface improvements. Conjunctival-limbal autologous transplantation is the treatment option of choice, but if it is not possible, living-related or cadaveric allogeneic transplants can be used. The benefits of LSCT outweigh the risks and burdens, as shown in Executive Summary Table 1. According to GRADE, these recommendations are strong with low- to very low-quality evidence.
Benefits, Risks, and Burdens – Nonpterygium Limbal Stem Cell Deficiency
Short- and long-term improvement in corneal surface (stable, normal corneal epithelium and decreased vascularization and opacity)
Improvement in vision (visual acuity and functional vision)
Long-term complications are experienced by 8% to 16% of patients
Risks associated with long-term immunosuppression for recipients of allogeneic grafts
Potential risk of induced LSCD in donor eyes
High cost of treatment (average cost per patient via OOC program is $57,583; estimated cost of procedure in Ontario is $2,291.48)
Costs are expressed in Canadian dollars.
GRADE of recommendation: Strong recommendation, low-quality or very low-quality evidence
benefits clearly outweigh risks and burdens
case series studies
strong, but may change if higher-quality evidence becomes available
Conjunctival-limbal autologous transplantations significantly reduced the risk of pterygium recurrence compared with CAU. No other comparison yielded statistically significant results, but CLAU reduced the risk of recurrence compared with MMC. However, the benefit of LSCT in Ontario is uncertain as the severity and recurrence of pterygium in Ontario is unknown. The complication rates suggest that CLAU is a safe treatment option to prevent the recurrence of pterygium. According to GRADE, given the balance of the benefits, risks, and burdens, the recommendations are very weak with moderate quality evidence, as shown in Executive Summary Table 2.
Benefits, Risks, and Burdens – Pterygium
Reduced recurrence; however, if recurrence is low in Ontario, this benefit might be minimal
Long-term complications rare
Increased cost
GRADE of recommendation: Very weak recommendations, moderate quality evidence.
uncertainty in the estimates of benefits, risks, and burden; benefits, risks, and burden may be closely balanced
very weak, other alternatives may be equally reasonable
PMCID: PMC3377549  PMID: 23074512
2.  Treatment of Popliteal Pterygium Using an Ilizarov External Fixator 
Clinics in Orthopedic Surgery  2009;1(4):236-239.
Popliteal pterygium syndrome is a rare congenital disorder that consists of popliteal webs and craniofacial, genitourinary and extremity anomalies. Only moderate successful surgical excision of the fibrotic band within the popliteal web has been reported because the nerves and vessels in the affected site are short and displaced into the web and they are attached to adjacent tissues. We performed hamstring tenotomy on the ischial tuberosity, tenotomy of the flexor hallucis longus and Z-lengthening of the Achilles tendon on the ankle in our patient, and this was followed by gradual correction using an Ilizarov external fixator. Full extension of the knee joint was achieved at the ninth postoperative week. However, some recurrence of flexion contracture was noted at two years follow-up. Gradual soft tissue lengthening with an Ilizarov external fixator can be one of the optimal procedures when excision of a fibrous band and Z-plasty are not possible due to severe adhesion of the nerves and vessels into a fibrotic band. However, a cautious approach is recommended when considering the high risk of recurrence.
PMCID: PMC2784965  PMID: 19956482
Popliteal pterygium syndrome; External fixator; Ilizarov
3.  Comparative analysis of IRF6 variants in families with Van der Woude syndrome and popliteal pterygium syndrome using public whole-exome databases 
Genetics in Medicine  2012;15(5):338-344.
Mutations in the transcription factor IRF6 cause allelic autosomal dominant clefting syndromes, Van der Woude syndrome, and popliteal pterygium syndrome. We compared the distribution of IRF6 coding and splice-site mutations from 549 families with Van der Woude syndrome or popliteal pterygium syndrome with that of variants from the 1000 Genomes and National Heart, Lung, and Blood Institute Exome Sequencing Projects.
We compiled all published pathogenic IRF6 mutations and performed direct sequencing of IRF6 in families with Van der Woude syndrome or popliteal pterygium syndrome.
Although mutations causing Van der Woude syndrome or popliteal pterygium syndrome were nonrandomly distributed with significantly increased frequencies in the DNA-binding domain (P = 0.0001), variants found in controls were rare and evenly distributed in IRF6. Of 194 different missense or nonsense variants described as potentially pathogenic, we identified only two in more than 6,000 controls. PolyPhen and SIFT (sorting intolerant from tolerant) reported 5.9% of missense mutations in patients as benign, suggesting that use of current in silico prediction models to determine function can have significant false negatives.
Mutation of IRF6 occurs infrequently in controls, suggesting that for IRF6 there is a high probability that disruption of the coding sequence, particularly the DNA-binding domain, will result in syndromic features. Prior associations of coding sequence variants in IRF6 with clefting syndromes have had few false positives.
PMCID: PMC3723330  PMID: 23154523
cleft; exome; mutation; popliteal pterygium; Van der Woude
4.  Mutations in IRF6 cause Van der Woude and popliteal pterygium syndromes 
Nature genetics  2002;32(2):285-289.
Interferon regulatory factor 6 (IRF6) belongs to a family of nine transcription factors that share a highly conserved helix–turn–helix DNA-binding domain and a less conserved protein-binding domain. Most IRFs regulate the expression of interferon-α and -β after viral infection1, but the function of IRF6 is unknown. The gene encoding IRF6 is located in the critical region for the Van der Woude syndrome (VWS; OMIM 119300) locus at chromosome 1q32–q41 (refs 2,3). The disorder is an autosomal dominant form of cleft lip and palate with lip pits4, and is the most common syndromic form of cleft lip or palate. Popliteal pterygium syndrome (PPS; OMIM 119500) is a disorder with a similar orofacial phenotype that also includes skin and genital anomalies5. Phenotypic overlap6 and linkage data7 suggest that these two disorders are allelic. We found a nonsense mutation in IRF6 in the affected twin of a pair of monozygotic twins who were discordant for VWS. Subsequently, we identified mutations in IRF6 in 45 additional unrelated families affected with VWS and distinct mutations in 13 families affected with PPS. Expression analyses showed high levels of Irf6 mRNA along the medial edge of the fusing palate, tooth buds, hair follicles, genitalia and skin. Our observations demonstrate that haploinsufficiency of IRF6 disrupts orofacial development and are consistent with dominant-negative mutations disturbing development of the skin and genitalia.
PMCID: PMC3169431  PMID: 12219090
5.  Popliteal pterygium syndrome: a clinical study of three families and report of linkage to the Van der Woude syndrome locus on 1q32 
Journal of Medical Genetics  1999;36(12):888-892.
Popliteal pterygium syndrome (PPS) is a rare autosomal dominant disorder, thought to occur with an incidence of approximately 1 in 300 000 live births. The main clinical manifestations are popliteal webbing, cleft lip, cleft palate, lower lip pits, syndactyly, and genital and nail anomalies. This report describes the clinical features in two families with PPS and one isolated case, showing the range of anomalies found both within and between the families. PPS has some features in common with Van der Woude syndrome (VWS), also inherited as an autosomal dominant condition, with cleft lip/palate and, more distinctively, lower lip pits. Although the gene for VWS has not yet been identified, it has been localised to within 1.6 cM in the region 1q32-41. To determine whether PPS and VWS represent allelic forms of the same gene, three families were genotyped for markers flanking and within the critical region. A multipoint lod score of 2.7 was obtained, with no evidence of recombination, supporting the hypothesis that these two disorders are allelic.

Keywords: pterygium; van der Woude syndrome; cleft lip; cleft palate
PMCID: PMC1734268  PMID: 10593995
6.  Escobar Syndrome (Multiple Pterygium Syndrome) Associated with Thoracic Kyphoscoliosis, Lordoscoliosis, and Severe Restrictive Lung Disease: A Case Report 
HSS Journal  2005;1(1):35-39.
Escobar syndrome or multiple pterygium syndrome is characterized by a web across every flexion crease in the extremities, most notably the popliteal space. In addition, this syndrome is associated with two other structural anomalies: a vertical talus and congenital lordoscoliosis. We present a case report of a patient with Escobar syndrome who was initially managed conservatively and subsequently had severe and debilitating progression and respiratory decompensation ultimately requiring surgical intervention.
Study Design
Case report.
After preoperative evaluation by a pediatrician, pulmonologist, and otolaryngologist, the patient underwent one-stage anterior and posterior spinal fusion with instrumentation as well as multiple osteotomies, rib resections, and vertebrectomies.
The patient’s postoperative course was complicated by wound necrosis requiring irrigation and debridement, a urinary tract infection, and a tracheostomy for persistent atelectasis. The patient eventually recovered from all complications. There were never any focal neurologic deficits. The patient had a 3-year follow-up with radiographically confirmed maintenance of correction. Fusion was obtained in the anterior and posterior segments. Clinically, the patient is able to stand upright, can participate in functional activities, and has not required any pain medication. The patient’s functional vital capacity improved from 23% predicted preoperatively to 60% predicted postoperatively.
Patients with severe spinal deformity secondary to Escobar syndrome can be successfully treated surgically. We propose early surgical intervention in this group to prevent curve progression, restrictive lung disease, and the need for complex salvage procedures.
PMCID: PMC2504136  PMID: 18751807
Escobar syndrome; spinal deformity; restrictive lung disease; multiple pterygium syndrome; lordoscoliosis
7.  Multiple pterygium syndrome. 
Journal of Medical Genetics  1981;18(6):451-455.
The multiple pterygium syndrome is a rare autosomal recessive condition characterised by arthrogryposis multiplex congenita, pterygia of the neck, fingers, and antecubital, popliteal, and intercrural areas, growth retardation, and facial, vertebral, and genital anomalies. We present two unrelated patients of 17 and 6 years of age, respectively, affected with this condition. We describe the natural history of their disorder since birth and review the spectrum of phenotypic variation of the multiple pterygium syndrome in 25 published cases.
PMCID: PMC1048792  PMID: 7334504
8.  A combined targeted mutation analysis of IRF6 gene would be useful in the first screening of oral facial clefts 
BMC Medical Genetics  2013;14:37.
Interferon Regulatory Factor 6 (IRF6) is a member of the IRF family of transcription factors. It has been suggested to be an important contributor to orofacial development since mutations of the IRF6 gene has been found in Van der Woude (VWS) and popliteal pterygium syndromes (PPS), two disorders that can present with isolated cleft lip and palate. The association between IRF6 gene and cleft lip and palate has also been independently replicated in many populations.
We screened a total of 155 Taiwanese patients with cleft lip with or without cleft palate (CL/P); 31 syndromic (including 19 VWS families), 44 non-syndromic families with at least two affected members, and 80 non-syndromic patients through a combined targeted, polymerase chain reaction (PCR)-based mutation analysis for the entire coding regions of IRF6 gene.
We found 11 mutations in 57.89% (11/19) of the VWS patients and no IRF6 mutation in 44 of the non-syndromic multiplex families and 80 non-syndromic oral cleft patients. In this IRF6 gene screening, five of these mutations (c.290 A>G, p.Tyr97Cys; c.360-375 16 bp deletion, p.Gln120HisfsX24; c.411_412 insA, p.Glu136fsX3; c.871 A>C, p.Thr291Pro; c.969 G>A, and p.Trp323X) have not been reported in the literature previously. Exon deletion was not detected in this series of IRF6 gene screening.
Our results confirm the crucial role of IRF6 in the VWS patients and further work is needed to explore for its function in the non-syndromic oral cleft with vary clinical features.
PMCID: PMC3606492  PMID: 23510002
IRF6 gene; Mutation analyses; Orofacial clefts
9.  Ankyloblepharon filiforme adnatum. 
Two cases of ankyloblepharon filiforme adnatum in siblings are presented. One sib had associated cleft lip and palate, the other had bilateral syndactyly of the second and third toes. Father, paternal grandmother, and great-grandmother all had bilateral syndactyly of the second and third toes. Cases of ankyloblepharon filiforme adnatum reported in the ophthalmic literature are reviewed as are cases of ankyloblepharon occurring as part of the popliteal pterygium syndrome. It is postulated that the association of ankyloblepharon with other abnormalities may be part of the spectrum of the popliteal pterygium syndrome with autosomal dominant inheritance, incomplete penetrance, and variable expressivity.
PMCID: PMC1043413  PMID: 218608
10.  Missense mutations that cause Van der Woude syndrome and popliteal pterygium syndrome affect the DNA-binding and transcriptional activation functions of IRF6 
Human Molecular Genetics  2008;18(3):535-545.
Cleft lip and cleft palate (CLP) are common disorders that occur either as part of a syndrome, where structures other than the lip and palate are affected, or in the absence of other anomalies. Van der Woude syndrome (VWS) and popliteal pterygium syndrome (PPS) are autosomal dominant disorders characterized by combinations of cleft lip, CLP, lip pits, skin-folds, syndactyly and oral adhesions which arise as the result of mutations in interferon regulatory factor 6 (IRF6). IRF6 belongs to a family of transcription factors that share a highly conserved N-terminal, DNA-binding domain and a less well-conserved protein-binding domain. To date, mutation analyses have suggested a broad genotype–phenotype correlation in which missense and nonsense mutations occurring throughout IRF6 may cause VWS; in contrast, PPS-causing mutations are highly associated with the DNA-binding domain, and appear to preferentially affect residues that are predicted to interact directly with the DNA. Nevertheless, this genotype–phenotype correlation is based on the analysis of structural models rather than on the investigation of the DNA-binding properties of IRF6. Moreover, the effects of mutations in the protein interaction domain have not been analysed. In the current investigation, we have determined the sequence to which IRF6 binds and used this sequence to analyse the effect of VWS- and PPS-associated mutations in the DNA-binding domain of IRF6. In addition, we have demonstrated that IRF6 functions as a co-operative transcriptional activator and that mutations in the protein interaction domain of IRF6 disrupt this activity.
PMCID: PMC2638798  PMID: 19036739
11.  Familial Ectrodactyly Syndrome in a Nigerian Child: A Case Report 
Oman Medical Journal  2011;26(4):275-278.
Ectrodactyly, also known as Split-Hand/Split-Foot Malformation (SHFM) is a rare genetic condition characterized by defects of the central elements of the autopod. It has a prevalence of 1:10,000-1:90,000 worldwide. The X-linked and autosomal dominant types have been described. It can occur as an isolated malformation or in combination with other anomalies, such as tibial aplasia, craniofacial defects, and genitourinary abnormalities. Ectrodactyly-ectodermal dysplasia-clefting syndrome (EEC) is an example of ectrodactyly syndrome accompanied by multiple organ defects. Ectrodactyly has been reported in Africa, especially in several families in remote areas of central Africa but there has not been any published work on ectrodactyly in Nigeria. A baby was born in Ilorin, North Central Zone of Nigeria, with an uneventful prenatal and delivery history but was noticed to have malformation of the two hands and the two lower limbs at birth which are replica of the father’s malformation. We present this case to highlight familial ectrodactyly in Nigeria and prepare us to improve upon simple prenatal diagnosis and management of the challenges associated with patients with congenital malformation in Nigeria and other developing countries.
PMCID: PMC3191709  PMID: 22043435
Familial; Ectrodactyly; Congenital
12.  Comparative analysis of IRF6 variants in families with Van der Woude syndrome and popliteal pterygium syndrome using public whole exome databases 
IRF6 is a transcription factor that, when mutated, causes allelic autosomal dominant clefting syndromes, Van der Woude syndrome (VWS) and popliteal pterygium syndrome (PPS). We compared the distribution of IRF6 coding and splice site mutations from 549 VWS or PPS families to that of variants from the 1000 Genomes and NHLBI Exome Sequencing Projects.
We compiled all published pathogenic IRF6 mutations and performed direct sequencing of IRF6 in VWS/PPS families.
While mutations causing VWS/PPS were non-randomly distributed with significantly increased frequencies in the DNA-binding domain (p=0.0001), variants found in controls were rare and evenly distributed in IRF6. Out of 194 different missense or nonsense variants described as potentially pathogenic, we identified only two in over 6000 controls. 5.9% of missense mutations in patients were reported by PolyPhen and SIFT as benign; suggesting that use of current in silico prediction models to determine function can have significant false negatives.
Mutation of IRF6 occurs infrequently in controls, suggesting that for IRF6 there is a high probability that disruption of the coding sequence, particularly the DNA-binding domain, will result in syndromic features. Prior associations of coding sequence variants in IRF6 with clefting syndromes have had few false positives.
PMCID: PMC3723330  PMID: 23154523
Van der Woude; exome; cleft; popliteal pterygium; mutation
13.  Novel IRF6 mutations in families with Van Der Woude syndrome and popliteal pterygium syndrome from sub-Saharan Africa 
Orofacial clefts (OFC) are complex genetic traits that are often classified as syndromic or nonsyndromic clefts. Currently, there are over 500 types of syndromic clefts in the Online Mendelian Inheritance in Man (OMIM) database, of which Van der Woude syndrome (VWS) is one of the most common (accounting for 2% of all OFC). Popliteal pterygium syndrome (PPS) is considered to be a more severe form of VWS. Mutations in the IRF6 gene have been reported worldwide to cause VWS and PPS. Here, we report studies of families with VWS and PPS in sub-Saharan Africa. We screened the DNA of eight families with VWS and one family with PPS from Nigeria and Ethiopia by Sanger sequencing of the most commonly affected exons in IRF6 (exons 3, 4, 7, and 9). For the VWS families, we found a novel nonsense variant in exon 4 (p.Lys66X), a novel splice-site variant in exon 4 (p.Pro126Pro), a novel missense variant in exon 4 (p.Phe230Leu), a previously reported splice-site variant in exon 7 that changes the acceptor splice site, and a known missense variant in exon 7 (p.Leu251Pro). A previously known missense variant was found in exon 4 (p.Arg84His) in the PPS family. All the mutations segregate in the families. Our data confirm the presence of IRF6-related VWS and PPS in sub-Saharan Africa and highlights the importance of screening for novel mutations in known genes when studying diverse global populations. This is important for counseling and prenatal diagnosis for high-risk families.
PMCID: PMC4049366  PMID: 24936515
IRF6; popliteal pterygium syndrome; sub-Saharan Africa; Van der Woude syndrome
14.  The Greig cephalopolysyndactyly syndrome 
The Greig cephalopolysyndactyly syndrome (GCPS) is a pleiotropic, multiple congenital anomaly syndrome. It is rare, but precise estimates of incidence are difficult to determine, as ascertainment is erratic (estimated range 1–9/1,000,000). The primary findings include hypertelorism, macrocephaly with frontal bossing, and polysyndactyly. The polydactyly is most commonly preaxial of the feet and postaxial in the hands, with variable cutaneous syndactyly, but the limb findings vary significantly. Other low frequency findings include central nervous system (CNS) anomalies, hernias, and cognitive impairment.
GCPS is caused by loss of function mutations in the GLI3 transcription factor gene and is inherited in an autosomal dominant pattern. The disorder is allelic to the Pallister-Hall syndrome and one form of the acrocallosal syndrome.
Clinical diagnosis is challenging because the findings of GCPS are relatively non-specific, and no specific and sensitive clinical have been delineated. For this reason, we have proposed a combined clinical-molecular definition for the syndrome. A presumptive diagnosis of GCPS can be made if the patient has the classic triad of preaxial polydactyly with cutaneous syndactyly of at least one limb, hypertelorism, and macrocephaly. Patients with a phenotype consistent with GCPS (but which may not manifest all three attributes listed above) and a GLI3 mutation may be diagnosed definitively with GCPS. In addition, persons with a GCPS-consistent phenotype who are related to a definitively diagnosed family member in a pattern consistent with autosomal dominant inheritance may be diagnosed definitively as well. Antenatal molecular diagnosis is technically straightforward to perform.
Differential diagnoses include preaxial polydactyly type 4, the GCPS contiguous gene syndrome, acrocallosal syndrome, Gorlin syndrome, Carpenter syndrome, and Teebi syndrome.
Treatment of the disorder is symptomatic, with plastic or orthopedic surgery indicated for significant limb malformations.
The prognosis for typically affected patients is excellent. There may be a slight increase in the incidence of developmental delay or cognitive impairment. Patients with large deletions that include GLI3 may have a worse prognosis.
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PMCID: PMC2397380  PMID: 18435847
15.  Expression analysis of human pterygium shows a predominance of conjunctival and limbal markers and genes associated with cell migration 
Molecular Vision  2009;15:2421-2434.
Pterygium is a vision-impairing fibrovascular lesion that grows across the corneal surface and is associated with sunlight exposure. To increase our understanding of the cells types involved in pterygium, we have used expressed sequence tag analysis to examine the transcriptional repertoire of isolated pterygium and to identify marker genes for tissue origin and cell migration.
An unnormalized unamplified cDNA library was prepared from 15 pooled specimens of surgically removed pterygia as part of the NEIBank project. Gene expression patterns were compared with existing data for human cornea, limbus, and conjunctiva, and expression of selected genes was verified by immunofluorescence localization in normal eye ocular surface and in pterygium.
Sequence analysis of 2,976 randomly selected clones produced over 1,800 unique clusters, potentially representing single genes. The most abundant complementary DNAs from pterygium include clusterin, keratins 13 (Krt13) and 4 (Krt4), S100A9/calgranulin B, and spermidine/spermine N1-acetyltransferase (SAT1). Markers for both conjunctiva (such as keratin 13/4 and AQP3) and corneal epithelium (such as keratin 12/3 and AQP5) were present. Immunofluorescence of Krt12 and 13 in the normal ocular surface showed specificity of Krt12 in cornea and Krt13 in conjunctival and limbal epithelia, with a fairly sharp boundary at the limbal–corneal border. In the pterygium there was a patchy distribution of both Krt12 and 13 up to a normal corneal epithelial region specific for Krt12. Immunoglobulins were also among the prominently expressed transcripts. Several of the genes expressed most abundantly in excised pterygium, particularly S100A9 and SAT1, have roles in cell migration. SAT1 exerts its effects through control of polyamine levels. IPENSpm, a polyamine analogue, showed a significant ability to reduce migration in primary cultures of pterygium. A number of genes highly expressed in cornea were not found in pterygium (several small leucine-rich proteoglycan family members) or were expressed at considerably lower levels (ALDH3A1 and decorin).
The expression pattern of keratins and other markers in pterygium most closely resemble those of conjunctival and limbal cells; some corneal markers are present, notably Krt12, but at lower levels than equivalent conjunctival markers. Our data are consistent with the model of pterygium developing from the migration of conjunctival- and limbal-like cells into corneal epithelium. Identification of genes with roles in cell migration suggests potential therapeutic targets. In particular, the ability of polyamine analogues to reduce migration in primary cultures of pterygium presents a possible approach to slowing pterygium growth.
PMCID: PMC2785720  PMID: 19956562
16.  Epidemiology of pterygium in Victoria, Australia 
AIM—To describe the prevalence of and risk factors for pterygium in a population based sample of residents of the Australian state of Victoria who were aged 40 years and older.
METHODS—The strata comprised nine randomly selected clusters from the Melbourne statistical division, 14 nursing homes randomly selected from the nursing homes within a 5 kilometre radius of the nine Melbourne clusters, and four randomly selected clusters from rural Victoria. Pterygium was measured in millimetres from the tip to the middle of the base. During an interview, people were queried about previous ocular surgery, including surgical removal of pterygium, and their lifetime exposure to sunlight.
RESULTS—5147 people participated. They ranged in age from 40 to 101 years and 2850 (55.4%) were female. Only one person in the Melbourne cohort reported previous pterygium surgery, and seven rural residents reported previous surgery; this information was unavailable for the nursing home residents. Pterygium was present upon clinical examination in 39 (1.2%) of the 3229 Melbourne residents who had the clinical examination, six (1.7%) of the nursing home residents, and 96 (6.7%) of the rural residents. The overall weighted population rate in the population was 2.83% (95% CL 2.35, 3.31). The independent risk factors for pterygium were found to be age (OR=1.23, 95% CL=1.06, 1.44), male sex (OR=2.02, 95% CL=1.35, 3.03), rural residence (OR=5.28, 95% CL=3.56, 7.84), and lifetime ocular sun exposure (OR=1.63, 95% CL=1.18, 2.25). The attributable risk of sunlight and pterygium was 43.6% (95% CL=42.7, 44.6). The result was the same when ocular UV-B exposure was substituted in the model for broad band sun exposure.
CONCLUSION—Pterygium is a significant public health problem in rural areas, primarily as a result of ocular sun exposure.

PMCID: PMC1723391  PMID: 10684840
17.  Winglets of the eye: dominant transmission of early adult pterygium of the conjunctiva. 
Journal of Medical Genetics  1990;27(6):392-394.
A pterygium, a wing-like thickening, of the bulbar conjunctiva is of environmental interest because it can occur on prolonged exposure to wind and weather. We describe a family with pterygium in two generations without a history of unusual exposure to the elements. There were six females and five males (including a set of male twins) with seven bilateral and four unilateral pterygia. The onset was unique in being in early adulthood, from the late teens through the twenties. This new genetic form can be distinguished by the age of onset from congenital and mid-adult pterygia, which are inherited as autosomal dominant traits. Irrespective of age, the treatment of conjunctival pterygium is surgical excision.
PMCID: PMC1017140  PMID: 2359104
18.  Popliteal pterygium syndrome: a phenotypic and genetic analysis. 
Journal of Medical Genetics  1978;15(1):35-42.
Two additional families with popliteal pterygium syndrome are presented. Using previously published pedigrees, as well as the ones reported here, evidence is presented that supports an autosomal dominant mode of inheritance for this syndrome. Analysis of previous familial cases showed a large degree of between and within-family variation. The segregation analysis supports the dominant hypothesis (P=0.5).
PMCID: PMC1012821  PMID: 633318
19.  Escobar syndrome in three male patients of same family 
We describe three male individuals from a consanguineous south Indian family affected with the multiple pterygium syndrome (Escobar syndrome). Common clinical features included short stature, multiple pterygium, skeletal anomalies, and normal intelligence. The first report of this condition was made in 1902 from this same place (Pondicherry) and the disease received its present popular name Escobar syndrome in 1982. The genetic defect for this condition was identified in 2006 as mutation in the fetal acetylcholine receptor.
PMCID: PMC3144683  PMID: 21814339
Escobar syndrome; familial; multiple pterygium syndrome
20.  Pterygium syndrome. 
Journal of Medical Genetics  1976;13(3):249-251.
The pterygium syndrome consists of the neck, the antecubital fossae and the popliteal regions together with flexion deformities of the limb joints and anomalies of the vertebrae. A family, three offspring of which appear to be affected with the same disorder, is presented. All three are female; there is also a normal female child of the same union.
PMCID: PMC1013404  PMID: 933128
21.  An autosomal dominant multiple pterygium syndrome. 
Journal of Medical Genetics  1988;25(2):96-103.
Three sibs and their mother with features of a multiple pterygium syndrome are reported. Inheritance in this family is consistent with autosomal dominant inheritance with great variation in severity between affected subjects. The importance of examining other family members closely in cases of multiple pterygium is emphasised.
PMCID: PMC1015450  PMID: 2831369
22.  Fraser syndrome and cryptophthalmos: review of the diagnostic criteria and evidence for phenotypic modules in complex malformation syndromes 
Journal of Medical Genetics  2002;39(9):623-633.
Fraser syndrome is characterised by cryptophthalmos, cutaneous syndactyly, malformations of the larynx and genitourinary tract, craniofacial dysmorphism, orofacial clefting, mental retardation, and musculoskeletal anomalies. The inheritance is autosomal recessive. No diagnostic cytogenetic abnormalities have been documented in affected patients, and no molecular genetic studies have been reported. We have reviewed 117 cases diagnosed as Fraser syndrome or cryptophthalmos published since the comprehensive review of Thomas et al in 1986 in order to validate the published diagnostic criteria and to delineate the phenotype associated with this syndrome.
Our series showed more females (57/117) than males and consanguinity was present in 29/119 (24.8%). Eighty-eight patients satisfied the diagnostic criteria for Fraser syndrome (75%). Cryptophthalmos was present in 103/117 (88%), syndactyly in 72/117 (61.5%), and ambiguous genitalia in 20/117 (17.1%). Ear malformations were recorded in 69/117 (59%), and renal agenesis in 53/117 (45.3%). Use of the published diagnostic criteria excluded several patients with cryptophthalmos and one or more physical feature(s) consistent with Fraser syndrome. The frequency of additional anomalies in our series was also higher than previously reported (for example, imperforate anus or anal stenosis were found in 34/117 (29%) compared with 2/124 (2%) in the series of Thomas et al (1986) and choanal stenosis or atresia was present in 7/117 (6%) compared to 0/124. These findings emphasise the clinical variability associated with Fraser syndrome and support genetic heterogeneity of the syndrome. We also noted patterns of anomalies (for example, bicornuate uterus with imperforate anus or anal stenosis and renal malformations) that are found in other syndromes and associations without cryptophthalmos, suggesting that common modifier genes may explain some of the phenotypic variation in Fraser syndrome.
PMCID: PMC1735240  PMID: 12205104
23.  Search for Genetic Modifiers of IRF6 and Genotype-Phenotype Correlations in Van der Woude and Popliteal Pterygium Syndromes 
Van der Woude syndrome is the most common form of syndromic orofacial clefting, accounting for 1-2% of all patients with cleft lip and/or cleft palate. Van der Woude and popliteal pterygium syndromes are caused by mutations in IRF6, but phenotypic variability within and among families with either syndrome suggests that other genetic factors contribute to the phenotypes. The aim of this study was to identify common variants acting as genetic modifiers of IRF6 as well as genotype-phenotype correlations based on mutation type and location. We identified an association between mutations in the DNA-binding domain of IRF6 and limb defects (including pterygia). Although we did not detect formally significant associations with the genes tested, borderline associations suggest several genes that could modify the VWS phenotype, including FOXE1, TGFB3, and TFAP2A. Some of these genes are hypothesized to be part of the IRF6 gene regulatory network and may suggest additional genes for future study when larger sample sizes are also available. We also show that families with the Van der Woude phenotype but in whom no mutations have been identified have a lower frequency of cleft lip, suggesting there may be locus and/or mutation class differences in Van der Woude syndrome.
PMCID: PMC3898350  PMID: 23949966
Modifier gene; Van der Woude; popliteal pterygium; cleft; lip pit
24.  A Case of Popliteal Artery Entrapment Syndrome with Chronic Total Occlusion 
Annals of Vascular Diseases  2010;3(2):157-159.
Popliteal artery entrapment syndrome (PAES) is rare congenital anomaly that occurs due to compression of the popliteal artery by adjacent musculotendinous structures. We report a 54-year-old woman with PAES of total popliteal arterial occlusion was successfully treated by release of the muscle bundle and reconstruction of the popliteal artery. Pathologic examination revealed that the extracted portion of the popliteal artery had chronic total occlusion with fibrosis and destruction of internal elastic membrane. We should deliberate whether we reconstruct the popliteal artery in addition to release of the aberrant muscle bundle due to the preoperative examination to prevent the reoperation.
PMCID: PMC3595758  PMID: 23555405
popliteal artery entrapment syndrome; chronic total occlusion; CT angiography
25.  Interferon Regulatory Factor 6 (IRF6) and Fibroblast Growth Factor Receptor 1 (FGFR1) Contribute to Human Tooth Agenesis 
Phenotypic characteristics expressed in syndromes give clues to the factors involved in the cause of isolated forms of the same defects. We investigated two genes responsible for craniofacial syndromes, FGFR1 and IRF6, in a collection of families with isolated tooth agenesis. Cheek swab samples were obtained for DNA analysis from 116 case/parent trios. Probands had at least one developmentally missing tooth, excluding third molars. In addition, we studied 89 cases and 50 controls from Ohio to replicate any positive findings. Genotyping was performed by kinetic polymerase chain-reaction or TaqMan assays. Linkage disequilibrium analysis and transmission distortion of the marker alleles were performed. The same variants in the IRF6 gene that are associated with isolated orofacial clefts are also associated with human tooth agenesis (rs861019, P = 0.058; rs17015215—V274I, P = 0.0006; rs7802, P = 0.004). Mutations in IRF6 cause Van der Woude and popliteal pterygium syndromes. The craniofacial phenotypic characteristics of these syndromes include oral clefts and preferential tooth agenesis of incisors and premolars, besides pits on the lower lips. Also it appears that preferential premolar agenesis is associated with FGFR1 (P = 0.014) and IRF6 (P = 0.002) markers. There were statistically significant data suggesting that IRF6 interacts not only with MSX1 (P = 0.001), but also with TGFA (P = 0.03).
PMCID: PMC2570343  PMID: 17318851
hypodontia; oligodontia; cleft lip and palate; orofacial clefts; Kallmann syndrome; Van der Woude syndrome; PAX9; MSX1; TGFA; paired-box; muscle segment; transforming growth factor alpha

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