Ocular genetic disease in the Middle East

Centered on the Arabian Peninsula, the Middle East encompasses Northern Africa to Western Asia. Primarily Arab and historically tribal, populations from this region often practice customary intrafamilial marriage (consanguinity), intratribal marriage (endogamy), and a preference for many offspring. These social factors increase the frequency of homozygosity, including homozygosity for gene mutation and thus for recessive ocular disease. This review highlights recent studies of ocular genetic disease in the Middle East.

Among modern molecular genomic/genetic strategies, homozygosity mapping as a method to guide candidate gene analysis has been a powerful technique for the Middle East. Studies from the region have enhanced our understanding of ocular genetic conditions that are more common worldwide (such as pediatric glaucoma, pediatric cataract, and retinal dystrophy/dysfunction), rare worldwide (such as cornea plana, brittle cornea syndrome, and posterior microphthalmos), and currently only reported on the Arabian Peninsula (such as microcornea with myopic chorioretinal degeneration and telecanthus, familial retinal arterial macroaneurysms, and spherophakia with short stature). For some patients diagnosed with non-syndromic cataract or retinal dystrophy, genomic/genetic analysis uncovered recessive mutation in a syndrome gene and phenotypic reassessment confirmed the presence of the undiagnosed syndrome in the tested patients.

Recent studies from the Middle East, many of which employed homozygosity mapping, have improved phenotype-genotype correlations for common and rare ocular genetic disease. In some instances genetic diagnosis revealed an undiagnosed syndrome. Reports of ocular genetic conditions thus far unique to the region have suggested novel ocular developmental pathways.