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

The aim was to define the natural history of hearing loss in Usher syndrome type IIa compared to non-IIa. People with Usher syndrome type 11 show moderate-to-severe hearing loss, normal balance and retinitis pigmentosa. Several genes cause Usher syndrome type II. Our subjects formed two genetic groups: (1) subjects with Usher syndrome type IIa with a mutation and/or linkage to the Usher IIa gene; (2) subjects with the Usher 11 phenotype with no mutation and/or linkage to the Usher IIa gene. Four hundred and two audiograms of 80 Usher Ha subjects were compared with 435 audiograms of 87 non-IIa subjects. Serial audiograms with intervals of greater than or equal to5 years were examined for progression in 109 individuals. Those with Usher syndrome type IIa had significantly worse hearing thresholds than those with non-IIa Usher syndrome after the second decade. The hearing loss in Usher syndrome type IIa was found to be more progressive, and the progression started earlier than in non-IIa Usher syndrome. This suggests an auditory phenotype for Usher syndrome type IIa that is different from that of other types of Usher syndrome II. Thus, this is to our knowledge one of the first studies showing a genotype-phenotype auditory cot relation.