[Audiological findings and mitochondrial DNA mutation in a large family with matrilineal sensorineural hearing loss].

OBJECTIVE

To explore audiological features of matrilineal non-syndromic deafness and its molecular mechanism.

METHODS

A large family with 41 members having inherited deafness was studied. Complete history and the data of general and otolaryngological examinations were collected. All subjects were screened for mitochondrial DNA A1555G mutation by molecular analysis. Audiological evaluation included puretone audiometry, auditory brainstem responses and transiently evoked otoacoustic emissions.

RESULTS

All subjects were in good health generally. Molecular analysis showed that all maternal relatives with or without hearing loss harbored the A1555G mitochondrial mutation. No mutation was found among spouses and paternal relatives. Audiological results showed notable symmetric bilateral sensorineural hearing loss in 17 of 20 maternal relatives, in which 5 cases had a progressive hearing loss in the recent 11 years. The age of appearance of hearing loss ranged from 1 to 50 years.

CONCLUSION

All hearing-impaired subjects of this family had late-onset sensorineural hearing loss. Most of which were progressive. The A1555G mitochondrial mutation in the 12S rRNA gene is responsible for the disorder. Other factors, such as nuclear genes or environmental determinants, may influence the clinical expression of mutant mtDNA.