Prevalence of 2314delG mutation in Spanish patients with Ushersyndrome type II (USH2).

The Usher syndrome (USH) is a group of autosomalrecessive diseases characterized by congenital sensorineural hearing lossand retinitis pigmentosa. Three clinically distinct forms of Usher syndromehave so far been recognized and can be distinguished from one another by assessingauditory and vestibular function. Usher syndrome type II (USH2) patients havecongenital moderate-to-severe nonprogressive hearing loss, retinitis pigmentosa,and normal vestibular function. Genetic linkage studies have revealed geneticheterogeneity among the three types of USH, with the majority of USH2 familiesshowing linkage to the USH2A locus in 1q41. The USH2A gene (MIM 276901) hasbeen identified: three mutations, 2314delG, 2913delG, and 4353-54delC, wereinitially reported in USH2A patients, the most frequent of which is the 2314delGmutation. It has been reported that this mutation can give rise to typicaland atypical USH2 phenotypes. USH2 cases represent 62% of all USH cases inthe Spanish population, and 95% of these cases have provided evidence of linkageto the USH2A locus. In the present study, the three reported mutations wereanalyzed in 59 Spanish families with a diagnosis of USH type II. The 2314delGwas the only mutation identified in our population: it was detected in 25%of families and 16% of USH2 chromosomes analyzed. This study attempts to estimatethe prevalence of this common mutation in a homogeneous Spanish population. [ABSTRACT FROM AUTHOR]