Markedly different clinical features in 2 diabetes mellitus patients with extremely high tissue levels of the mitochondrial DNA A3243G mutation.

BACKGROUND Mitochondrial DNA (mtDNA) A3243G mutation is one of the major causative factors of mitochondrial diabetes mellitus. We found that tissues from 2 of 142 diabetes mellitus patients showed extremely high levels of the mutation. OBJECTIVE To investigate the level of the mutation in each tissue and to find the relationship between the mutation level and clinical features of the patients. METHODS Patient 1 was a 51-year-old woman, diagnosed as having diabetes mellitus at the age of 17, and was admitted to hospital because of cerebral infarction. Patient 2 was an 82-year-old woman who was admitted because of respiratory failure. mtDNA A3243G levels were measured in tissues collected at autopsy. RESULTS In patient 1, mtDNA A3243G levels were found to vary among the tissues. The patient's highest mtDNA A3243G value was 42% and the lowest value was 9%, whereas the level in most individuals is usually less than 1%. Although patient 2 did not exhibit serious clinical symptoms of diabetes mellitus, the mtDNA A3243G level was extremely high in all of the tissues surveyed (range 32-47%). CONCLUSION Although both patients showed high levels of the mtDNA A3243G mutation, their clinical conditions differed greatly. Thus, mitochondrial diabetes mellitus patients may show a wide variety of clinical features and large variations in life span.