Branchio-oculo-facial and branchio-oto-renal syndromes are distinct entities

A New Case and Comprehensive Review of the Ophthalmic Manifestations of 172 Individuals With Branchio-Oculo-Facial Syndrome

PURPOSE

To review the literature on branchio-oculo-facial syndrome and describe a new case.

METHODS

A girl presented with a de novo pathogenic mutation in the TFAP2A gene consistent with branchiooculo-facial syndrome. A systematic review was also performed to characterize the eye manifestations associated with the syndrome.

RESULTS

A total of 172 total patients were identified from the literature. Among these, 102 patients received molecular confirmation. The most common pathogenic variants reported were p.R255G, p.A256V, p.R254W, and p.G251E. Common eye abnormalities associated with the syndrome in total combined cases (represents individuals with a clinical diagnosis only of branchiooculo-facial syndrome plus those who additionally had molecular confirmation of the syndrome from genetic testing) were nasolacrimal duct stenosis (n = 98, 57%), coloboma (n = 76, 46%), anophthalmia/microphthalmia (n = 64, 37%), and cataracts (n = 27, 16%).

CONCLUSIONS

This analysis provides a comprehensive review of genetic variants and ophthalmic findings to characterize the most common eye manifestations associated with branchio-oculo-facial syndrome. The report provides incentive to further investigate TFAP2A variants and identify genotype-phenotype correlations. [J Pediatr Ophthalmol Strabismus. 20XX;XX(X):XX-XX.].

Detailed analysis of chick optic fissure closure reveals Netrin-1 as an essential mediator of epithelial fusion

Epithelial fusion underlies many vital organogenic processes during embryogenesis. Disruptions to these cause a significant number of human birth defects, including ocular coloboma. We provide robust spatial-temporal staging and unique anatomical detail of optic fissure closure (OFC) in the embryonic chick, including evidence for roles of apoptosis and epithelial remodelling. We performed complementary transcriptomic profiling and show that Netrin-1 (NTN1) is precisely expressed in the chick fissure margin during fusion but is immediately downregulated after fusion. We further provide a combination of protein localisation and phenotypic evidence in chick, humans, mice and zebrafish that Netrin-1 has an evolutionarily conserved and essential requirement for OFC, and is likely to have an important role in palate fusion. Our data suggest that NTN1 is a strong candidate locus for human coloboma and other multi-system developmental fusion defects, and show that chick OFC is a powerful model for epithelial fusion research.

Our bodies are made of many different groups of cells, which are arranged into tissues that perform specific roles. As tissues form in the embryo they must adopt precise three-dimensional structures, depending on their position in the body. In many cases this involves two edges of tissue fusing together to prevent gaps being present in the final structure.

In individuals with a condition called ocular coloboma some of the tissues in the eyes fail to merge together correctly, leading to wide gaps that can severely affect vision. There are currently no treatments available for ocular coloboma and in over 70% of patients the cause of the defect is not known. Identifying new genes that control how tissues fuse may help researchers to find what causes this condition and multiple other tissue fusion defects, and establish whether these may be preventable in the future.

Much of what is currently known about how tissues fuse has come from studying mice and zebrafish embryos. Although the extensive genetic tools available in these ‘models’ have proved very useful, both offer only a limited time window for observing tissues as they fuse, and the regions involved are very small. Chick embryos, on the other hand, are much larger than mouse or zebrafish embryos and are easier to access from within their eggs. This led Hardy et al. to investigate whether the developing chick eye could be a more useful model for studying the precise details of how tissues merge.

Examining chick embryos revealed that tissues in the base of their eyes fuse between five and eight days after the egg had been fertilised, a comparatively long time compared to existing models. Also, many of the genes that Hardy et al. found switched on in chick eyes as the tissues merged had previously been identified as being essential for tissue fusion in humans. However, several new genes were also shown to be involved in the fusing process. For example, Netrin-1 was important for tissues to fuse in the eyes as well as in other regions of the developing embryo.

These findings demonstrate that the chick eye is an excellent new model system to study how tissues fuse in animals. Furthermore, the genes identified by Hardy et al. may help researchers to identify the genetic causes of ocular coloboma and other tissue fusion defects in humans.

Branchiooculofacial syndrome and bilateral ectopic thymus: report of a family

Branchiooculofacial syndrome (BOFS) is a rare autosomal-dominant condition characterized by branchial cleft sinus and ophthalmologic and craniofacial abnormalities that can range from mild to severe forms. Ectopic thymus, an uncommon condition with just over 100 cases reported in the literature, is seen in BOFS. We report a family with BOFS affecting the mother and two daughters, showing the dominant inheritance and variable phenotypical expression of BOFS.

Craniofacial phenotype in the branchio-oculo-facial syndrome: four case reports

Branchio-oculo-facial syndrome represents a craniofacial disorder in which affected patients may develop a wide range of distinctive features that include cleft lip and/or palate, cervical aplastic skin defect, malformed pinna, and ocular anomalies. This study reports four new cases confirmed by the identification of mutations in the TFAP2A gene and describes in detail the findings in the craniofacial region. The four cases included two familial and two sporadic, and three have been followed since the birth. Two out of the four cases showed atypical features. One patient presented brainstem immaturity with dysregulation of sympathetic and parasympathetic systems, which have so far not been described in the literature and were associated with anxiety, panic attacks, and tiredness. Another patient had as an additional feature a hypoplastic thumb with distal implantation.

Clinical presentation and the presence of hearing impairment in branchio-oculo-facial syndrome: a new mutation in the TFAP2A gene

We report on the clinical presentation of branchio-oculo-facial (BOF) syndrome in 2 patients with mutations in the TFAP2A gene (OMIM 107580). This TFAP2A gene was recently shown to be involved in the causation of BOF syndrome. An overview of the literature on BOF syndrome is given based on clinical reports written in the period during which mutation analysis was not yet available for BOF syndrome. We also give descriptions of the mutations in the TFAP2A gene in our 2 new patients with BOF syndrome. Congenital conductive hearing impairments are described, including hearing rehabilitation and the results of ear surgery.

Mitral valve prolapse as a new finding in branchio-oto-renal syndrome

We report a patient and his family, who have branchio-oto-renal (BOR) syndrome and coexisting mitral valve prolapse. A literature review of BOR syndrome failed to identify any similar families and we report this as a new observation. During the preoperative assessment of a patient with BOR syndrome, tachycardia was noted and a cardiologic examination including echocardiography revealed mitral valve prolapse. Members of his extended family were investigated, including carrying out cardiology and otolaryngology examinations to determine whether they had signs of either BOR syndrome or cardiac problems. Mitral valve prolapse was identified in five (71.4%) of the seven BOR syndrome patients in the family. Deafness was present in all patients. Distribution of the other clinical findings of the BOR syndrome patients were as follows: branchial fistula in five (71.4%), preauricular pits in four (57.1%), ear deformity in two (28.5%), renal anomalies in three (42.8%), lacrimal duct anomaly in two (28.5%) and orbital anterior compartment anomaly in one (14.2%). We conclude that mitral valve prolapse can be associated with BOR syndrome. Further large studies are needed to clarify this association.

TFAP2A mutations result in branchio-oculo-facial syndrome

Branchio-oculo-facial syndrome (BOFS) is a rare autosomal-dominant cleft palate-craniofacial disorder with variable expressivity. The major features include cutaneous anomalies (cervical, infra- and/or supra-auricular defects, often with dermal thymus), ocular anomalies, characteristic facial appearance (malformed pinnae, oral clefts), and, less commonly, renal and ectodermal (dental and hair) anomalies. The molecular basis for this disorder is heretofore unknown. We detected a 3.2 Mb deletion by 500K SNP microarray in an affected mother and son with BOFS at chromosome 6p24.3. Candidate genes in this region were selected for sequencing on the basis of their expression patterns and involvement in developmental pathways associated with the clinical findings of BOFS. Four additional BOFS patients were found to have de novo missense mutations in the highly conserved exons 4 and 5 (basic region of the DNA binding domain) of the TFAP2A gene in the candidate deleted region. We conclude BOFS is caused by mutations involving TFAP2A. More patients need to be studied to determine possible genetic heterogeneity and to establish whether there are genotype-phenotype correlations.

Bradycardia with sevoflurane in siblings with Branchio-oto-renal syndrome

Branchio-oto-renal syndrome (BOR, Melnick-Fraser syndrome, MIM#113650) refers to a rare autosomal dominant disorder characterized by branchial cysts or fistulas, hearing loss, external ear malformation, preauricular pits and renal abnormalities. The authors present three episodes of significant bradycardia in two siblings diagnosed with BOR syndrome during the sevoflurane general anesthesia. There is no published experience of anesthesia with this syndrome. Bradycardia occurred variously at induction, maintenance and immediately prior to emergence and required surgical stimulation, atropine, or epinephrine to treat. We seek to raise awareness of the potential for bradycardia during the procedures in patients with this syndrome requiring volatile anesthesia, especially sevoflurane.

Exclusion of the branchio-oto-renal syndrome locus (EYA1) from patients with branchio-oculo-facial syndrome

In addition to craniofacial, auricular, ophthalmologic, and oral anomalies, the distinctive phenotype of the branchio-oculo-facial (BOF) syndrome (MIM 113620) includes skin defects in the neck or infra/supra-auricular region. These unusual areas of thin, erythematous wrinkled skin differ from the discrete cervical pits, cysts, and fistulas of the branchio-oto-renal (BOR) syndrome (MIM 113650). Although the BOF and BOR syndromes are sufficiently distinctive that they should not be confused, both can be associated with nasolacrimal duct stenosis, deafness, prehelical pits, malformed pinna, and renal anomalies. Furthermore, a reported father and son [Legius et al., 1990, Clin Genet 37:347-500] had features of both conditions. It was not clear whether they had an atypical presentation of either BOR or BOF syndrome, or represented a private syndrome. In light of these issues, we selected the BOR locus (EYA1) as a possible gene mutation for the BOF syndrome. In five BOF patients, there were no mutations detected in the EYA1 gene, suggesting that it is not allelic to the BOR syndrome.

Further delineation of the branchio-oculo-facial syndrome

We review 43 patients (15 new, 28 literature) with the branchio-oculo-facial (BOF) syndrome, which has a distinctive phenotype ranging from mild to severe forms, consisting of eye, ear, oral, and craniofacial anomalies. Virtually ubiquitous and possibly pathognomonic are the cervical/infra-auricular skin defects. Much less common are supra-auricular defects occurring as isolated anomalies or with cervical defects. Regardless of location, these lesions may have aplastic, "hemangiomatous," or otherwise abnormal overlying skin, and draining sinus fistulae. Renal malformations are frequent, but congenital heart and central nervous system defects are rare. Psychomotor performance is usually normal, but development delays, hypotonia, and visual, hearing, and speech problems are common. Autosomal dominant inheritance seems likely. Overlap between the BOF and branchio-otorenal syndromes has been observed, but elucidation of its molecular basis is not yet available. This article also discusses 5 patients with atypical manifestations considered to be possibly affected or probably unaffected, who are sufficiently unusual to be excluded from the final data analysis.

Branchio-oculo-facial syndrome: broadening the spectrum

We present 3 individuals, a mother, her son, and an unrelated child, with a number of manifestations reported in the branchio-oculo-facial syndrome (BOFS). The former 2 individuals lacked the ocular and branchial abnormalities normally encountered in this syndrome. However, unilateral renal agenesis was present in the first child, a defect infrequently found in the BOF syndrome. Both the mother and her son also had bilateral supra-auricular sinuses. These defects may represent persistence of the otic vesicle sinus tract. The second child has a mild expression of this condition, among the mildest reported in the literature. The BOFS appears to represent a spectrum involving the development of the optic vesicles, branchial arches, eyes, face, lips, and kidneys. The variations seen in this disorder and the overlap between this condition and the branchio-oto-renal syndrome may represent different mutations within a single gene or may be a contiguous gene deletion syndrome.