AUDIOLOGIC EVALUATION IN A FAMILY SHOWING DIABETES MELLITUS AND DEAFNESS ASSOCIATED WITH A MUTATION IN MITOCHONDRIAL DNA

Abstract

An A to G transition at nucleotide 3, 243 in the tRNA^{Leu (UUR)} gene of mitochondrial DNA has recently been identified as a pathogenic point mutation which is associated with diabetes mellitus and sensorineural deafness in several pedigrees. We have also reported a family showing the association of deafness and diabetes mellitus as the predominant clinical features with this mutation. Audiologic data from two patients in this family are presented. Both had a bilaterally symmetrical sensorineural hearing loss at all frequencies. As is often the case with deafness associated with a mitochondrial disorder, the pure-tone threshold values were maximal at high frequencies in both patients. The audiologic work-up presented not only cochlear characteristics but also signs suggestive of retrocochlear disturbance with poor speech discrimination scores as compared to pure-tone thresholds, although auditory brain-stem responses showed neither wave delay nor prolonged interpeak latencies. Caloric excitability was not impaired.