ADULT-ONSET DIABETES-MELLITUS AND NEUROSENSORY HEARING-LOSS IN MATERNAL RELATIVES OF MELAS PATIENTS IN A FAMILY WITH THE TRANSFER RNA(LEU)(UUR) MUTATION

We describe a family with three cases of ''clinically incomplete mitoc hondrial encephalomyopathy, lactic acidosis, and strokelike episodes ( MELAS) syndrome'' in which heteroplasmic tRNA(Leu(UUR)) mutation at nu cleotide 3243 of the mitochondrial DNA was present in three generation s. The amount of mutant genome varied among tissues: it was 60% in the kidney, 72% in the cardiac muscle, and 91% in the liver of the female proband's affected brother and 63% in the kidney, 71% in the cardiac muscle, and 71% in the liver of the female proband's perinatally decea sed son. The tRNA(Leu(UUR)), mutation was also carried by the siblings of the proband's affected mother. None of them had any clinical signs of MELAS syndrome. This syndrome has the new feature of being associa ted with adult-onset diabetes mellitus, neurosensory hearing loss, and short stature.