A patient with diabetes mellitus, cardiomyopathy, and a mitochondrial gene mutation: confirmation of a gene mutation in cardiac muscle.

A 44-year-old woman with diabetes mellitus, cardiomyopathy, and a mitochondrial gene mutation, was reported. She was diagnosed as having diabetes at 33 years of age and was treated with insulin. However, she stopped treatment 6 months later and had no medical care until she developed diabetic ketoacidosis at 41 years of age. She had diabetic foot, diabetic retinopathy, and nephropathy with low insulin secretory capacity, leading to insulin treatment. A point mutation of the mitochondrial tRNA(Leu(UUR)) gene was identified in peripheral leukocytes at 43 years of age, and sensorineural hearing impairment was detected at the same time. Her mother also suffered from diabetes mellitus with deafness and her son, who was not diabetic at age 19, had the same mitochondrial DNA (mtDNA) mutation. At 44 years of age, she developed congestive heart failure due to cardiomyopathy, and the same mtDNA mutation was identified in the cardiac muscle. Thus, it is very likely that in this patient, diabetes and cardiomyopathy was caused by the same abnormality, the point mutation of mitochondrial tRNA(Leu(UUR)) gene.