GAPO syndrome: four new patients with congenital glaucoma and myelinated retinal nerve fiber layer

Two siblings with GAPO syndrome: Ophthalmic presentation and histopathologic findings

BACKGROUND

GAPO syndrome (growth retardation, alopecia, pseudoanodontia, optic atrophy) is a rare, autosomal recessive connective tissue disorder with only 60 reported cases. Ophthalmic manifestations vary and include hypertelorism, optic atrophy, and glaucoma. There have been three reported cases of GAPO syndrome with craniosynostosis.

MATERIALS/METHODS

We describe two new siblings with GAPO syndrome and craniosynostosis and the first histopathologic analysis of Tenon's capsule and extraocular muscle in this syndrome.

RESULTS

Both siblings presented with papilledema and V-pattern strabismus in addition to the alopecia, brittle eyelashes, growth retardation, and pseudoanodontia that characterize GAPO syndrome. Cranial vault expansion, though successful, was complicated by lack of distinct periosteal layers, thin dural adherence to bone, and extensive venous bleeding. Tenons encountered during strabismus surgery was inelastic and highly vascular. Histopathological analysis revealed hyalinization of Tenon's and a thickened, homogenized, amorphous appearance, similar to the extracellular matrix abnormalities described in skin and other organs Histopathological analysis of extraocular muscle was, in contrast, unremarkable.

CONCLUSIONS

GAPO impacts the extracellular matrix of Tenon's resulting in inelasticity and hypervascularity. Ophthalmologists should be mindful of these aberrant characteristics when planning surgery in this population.

Whole exome sequencing identifies three novel mutations in ANTXR1 in families with GAPO syndrome

GAPO syndrome (OMIM#230740) is the acronym for growth retardation, alopecia, pseudoanodontia, and optic atrophy. About 35 cases have been reported, making it among one of the rarest recessive conditions. Distinctive craniofacial features including alopecia, rarefaction of eyebrows and eyelashes, frontal bossing, high forehead, mid-facial hypoplasia, hypertelorism, and thickened eyelids and lips make GAPO syndrome a clinically recognizable phenotype. While this genomic study was in progress mutations in ANTXR1 were reported to cause GAPO syndrome. In our study we performed whole exome sequencing (WES) for five affected individuals from three Turkish kindreds segregating the GAPO trait. Exome sequencing analysis identified three novel homozygous mutations including; one frame-shift (c.1220_1221insT; p.Ala408Cysfs*2), one splice site (c.411A>G; p.Gln137Gln), and one non-synonymous (c.1150G>A; p.Gly384Ser) mutation in the ANTXR1 gene. Our studies expand the allelic spectrum in this rare condition and potentially provide insight into the role of ANTXR1 in the regulation of the extracellular matrix.