Usher syndrome is a rare autosomal recessive genetic disorder characterized by the association of sensorineural deafness with retinitis pigmentosa and progressive vision loss. Prevalence is estimated at 1 in 6,000 to 20,000 worldwide. About 50% of all people who are deaf/blind have Usher syndrome. Clinically, Usher syndrome has three clinical subtypes, namely USH1, USH2 and USH3. Type 1 accounts for about 40% of cases, in which hearing loss is congenital, profound, nonprogressive, and typically associated with delayed development in motor skills, vestibular problems, and early onset of vision loss due to retinitis pigmentosa.There are seven distinct subtypes for USH1 from IA to IG. Clinical diagnosis for type 1 is based on findings of bilateral sensorineural hearing loss symmetric, congenital and profound.
There are currently 11 genes associated with Usher syndrome; type 1 can result from mutations in USH1C, MYO7A, CDH23, PCDH15 and USH1G genes. Usher syndrome type 1C was mapped to 11p15.1chromosome. More than 10 different mutations in USH1C gene that cause Usher syndrome type 1C have been identified.
See: [Saudi Arabia>Al Mutair et al., (2013)]
Al Mutair et al. (2013) described 15 patients from eight unrelated consanguineous families from Saudi Arabia and Kuwait with congenital hyperinsulinism and deafness. They analyzed the USH1C, ABCC8, and KCNJ11 genes by direct sequencing, multiplex ligation-dependent probe amplification, and microsatellite markers for the 15 patients. Fourteen of the patients had severe CHI with the need of subtotal pancreatectomy. All patients, except one who died early, were diagnosed with profound hearing loss with absent brain stem auditory-evoked response. A homozygous a 122.815-base pair deletion of USH1C exon 3–28 and ABCC8 exon 1–22, USH1C:c.(90+592)_ABCC8: c.(2694–528)del was found in all 10 patients with available DNA, and in the parents it was heterozygous.
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