Bilateral sensorineural hearing loss in members of a maternal lineage with mitochondrial point mutation

Pure-tone audiometry was carried out on members of a recently described maternal lineage with sensorineural deafness, harbouring a novel mitochondrial mutation in the gene for tRNA-ser(UCN). This revealed a characteristic pattern of symmetrical bilateral sensorineural hearing losses in each affected individual, predominantly affecting the high-frequencies, but with considerable variability between individuals. No clear correlation was observed between age and severity, but most subjects reported progressive worsening of their condition. Some members of the lineage were found to be heteroplasmic for the tRNA-ser(UCN) mutation. However, the severity of hearing loss was poorly correlated with the representation of the mutant mtDNA, indicating that other, as yet unidentified factors must be involved in the aetiology of this disorder.