BILATERAL SENSORINEURAL HEARING-LOSS IN MEMBERS OF A MATERNAL LINEAGEWITH A MITOCHONDRIAL POINT MUTATION

Pure-tone audiometry was carried out on members of a recently describe d maternal lineage with sensorineural deafness, harbouring a novel mit ochondrial mutation in the gene for tRNA-ser(UCN). This revealed a cha racteristic pattern of symmetrical bilateral sensorineural hearing los ses in each affected individual, predominantly affecting the high-freq uencies, but with considerable variability between individuals. No cle ar correlation was observed between age and severity, but most subject s reported progressive worsening of their condition. Some members of t he lineage were found to be heteroplasmic for the tRNA-ser(UCN) mutati on. However, the severity of hearing loss was poorly correlated with t he representation of the mutant mtDNA, indicating that other, as yet u nidentified factors must be involved in the aetiology of this disorder .