Objective: To discuss clinical features at diabetic subtype which is apparently caused by a single mutation in the mitochondrial tRNA(Leu(UUR)) gene.
Methods: According to WHO criteria of diabetes mellitus (DM), 130 patients with DM and the family history of DM (either NIDDM or IDDM) were screened by using genetic diagnosis. Clinical and laboratory analyses were made in three unrelated patients with the mutation in mtDNA and their relatives.
Results: Four unrelated subjects (3.1%) were detected with mutation at position 3243 of mitochondrial DNA. The nine diabetes patients from first degree relatives of three probands were also identified with the mutation, in which eight patients were associated with sensory hearing loss and required insulin therapy due to secondary failure to oral hypoglycemic agents. All these nine patients had a lower frequency of obesity in the past, and most of them had a mother with diabetes, were younger at diagnosis, and were generally accompanied by in paired insulin secretion.
Conclusion: Since the patients have the clinical characteristics of maternal transmission, hearing loss and impaired insulin secretion, we conclude that maternally inherited diabetes and deafness (MIDD) is a new diabetes subtype associated with a single mitochondrial mutation.