Frequency and clinical features of patients with sensorineural hearing loss associated with the A3243G mutation of the mitochondrial DNA in otorhinolaryngic clinics.

The A3243G mutation of the mitochondrial gene is a cause of maternally inherited diabetes and deafness. The aim of this study was to evaluate the frequency and clinical features of this mutation in patients with sensorineural hearing loss (SNHL) in otorhinolaryngic clinics. The frequency of the A3243G mutation in 230 patients with SNHL was 1.74% (4/230). Three of the four patients had diabetes mellitus (DM) and were already aware that they had the mutation. The other had cardiomyopathy but not DM, and proved to have the mutation in this study. The frequency of the mutation was 12.9% (4/31) in patients with a family history of possible maternal inheritance of SNHL, 10.3% (3/29) in patients with DM, and 50% (3/6) in patients with both. The age of onset of SNHL in these patients and their families was between their teens and their forties. The chance of diagnosing the A3243G mutation in patients with SNHL in otorhinolaryngic clinics is probably less than 1%. Association of DM, cardiomyopathy, a family history of possible maternal inheritance of SNHL, and an onset of SNHL between the teens and the forties are signs suggesting the mutation. These signs provide us with a reason for genetic testing for the mutation.