Mitochondrial 3243 BP mutation: A case report

Mitochondrial DNA (mtDNA) gene defects may play a role in the development of maternally inherited diabetes mellitus and deafness (MIDD). Mutation in the mitochondrial gene at position 3243 was recently identified in several pedigrees of diabetes mellitus and deafness. As the mitochondria play an important role in glucose-stimulated insulin secretion in pancreatic beta-cells, we therefore searched for this mutation in a non-consanguineous family with MIDD from Southern Italy. The mitochondrial 3243 bp mutation of the tRNALEU (UUR) gene was identified in one subject with deafness and Type 1B diabetes mellitus and in his mother. The mother was affected by Type 2 diabetes mellitus, deafness and cardiomyopathy. Our study points out the variable phenotypic expression of this mitochondrial mutation. This may suggest the presence of other mitochondrial or nuclear mutations required to modulate the phenotype.