Nonsyndromic hearing loss caused by a mitochondrial T7511C mutation.

Abstract

The aims of the present study were to identify a mutation in a Japanese family showing nonsyndromic sensorineural hearing loss and to relate the mutation to characteristics of patients, including audiovestibular findings. Familial cohort study. Mutation analysis was performed using genomic DNA extracted from blood samples. Subjects underwent audiovestibular examinations, including pure-tone audiograms, tympanometry, self-recording audiometry, acoustic reflex threshold, speech discrimination testing, evoked and distortion-product otoacoustic emissions, auditory brainstem responses, and caloric testing. We identified a T7511C mutation in the mitochondrial tRNA(Ser(UCN)) gene previously reported in one other family. The degree of heteroplasmy for the T7511C mutation ranged from 84% to 92%, and did not correlate with age at examination or severity of hearing loss. Extensive audiologic evaluation suggested both cochlear and retrocochlear involvement. Families with maternally transmitted nonsyndromic hearing loss should be investigated for mutations in the tRNA(Ser(UCN)) gene.