Audiological findings in Usher syndrome types IIa and II (non-IIa)

Abstract

The aim was to define the natural history of hearing lossin Usher syndrome type IIa compared to non-IIa. Peoplewith Usher syndrome type II show moderate-to-severehearing loss, normal balance and retinitis pigmentosa.Several genes cause Usher syndrome type II. Our subjectsformed two genetic groups: (1) subjects with Usher syndrometype IIa with a mutation and/or linkage to theUsher IIa gene; (2) subjects with the Usher II phenotypewith no mutation and/or linkage to the Usher IIa gene.Four hundred and two audiograms of 80 Usher IIa subjectswere compared with 435 audiograms of 87 non-IIasubjects. Serial audiograms with intervals of ≥5 yearswere examined for progression in 109 individuals. Thosewith Usher syndrome type IIa had significantly worsehearing thresholds than those with non-IIa Usher syndromeafter the second decade. The hearing loss in Ushersyndrome type IIa was found to be more progressive, andthe progression started earlier than in non-IIa Usher syndrome.This suggests an auditory phenotype for Ushersyndrome type IIa that is different from that of other typesof Usher syndrome II. Thus, this is to our knowledgeone of the first studies showing a genotype-phenotypeauditory correlation.