Usher syndrome in the United Arab Emirates.

Purpose: Usher syndrome, a common form of syndromic inherited retinal dystrophy in the Arabian Gulf, has not been molecularly defined in the United Arab Emirates. The current study addresses this gap in knowledge.

Methods: A retrospective case series of Emirati patients referred to the Ocular Genetics Clinic of Cleveland Clinic Abu Dhabi who (1) were clinically diagnosed with Usher syndrome and underwent genetic testing (whole exome sequencing, 2019 to 2023, inclusive) and (2) were identified to have biallelic pathogenic variants in Usher syndrome genes during the same time period.

Results: Ten probands (thirteen patients) were identified-seven probands (nine patients) with clinically diagnosed Usher syndrome and three additional probands (four patients) with biallelic homozygous variants. Among the seven probands initially diagnosed with Usher syndrome, six had different homozygous variants (three in , one in , and one in ), one had dual diagnoses rather than Usher syndrome (i.e. separate cause for retinal dystrophy and deafness), and one had no identifiable genetic cause. Regarding the three additional probands identified with homozygous variants, all three had retinitis pigmentosa only rather than Usher syndrome and all three had different variants.

Discussion: Clinically diagnosed Usher syndrome was genetically heterogenous without evidence for founder effect in this Emirati cohort. was the most common associated gene. Dual diagnosis rather than single cause can mimic Usher syndrome. Homozygous variants were not identified as a cause for Usher syndrome in this cohort but were a recurrent cause for retinitis pigmentosa without hearing impairment and without founder effect.