Maternally inherited diabetes and deafness: prevalence in a hospital diabetic population.

Maternally inherited diabetes and deafness (MIDD) is a new sub-type of diabetes and results from an A to G substitution at position 3243 of the mitochondrial tRNA(leu(UUR)) gene. This mutation is also associated with a neurological syndrome (MELAS). Recent studies have screened carefully selected diabetic populations and have reported MIDD prevalence rates ranging from undetectable to 60%. The aim of this work was to determine the importance of this sub-type in clinical practice by screening a routine hospital diabetic population. A total of 1440 patients (IDDM and NIDDM) of North European extraction attending two hospital diabetes services were initially screened by questionnaire. This identified 445 patients with one or more features of MIDD and/or MELAS and these subjects were then genotyped. Two patients were identified with the mutation giving a prevalence rate of 0.13% for the whole study population, and 0.45% for the sample with phenotypic features of MIDD. In conclusion, therefore, the 3243 mutation is associated with the phenotypically distinct MIDD sub-type, but this is rare in the routine hospital diabetic population.