Higher proportion of mitochondrial A3243G mutation in blood than in skeletal muscle in a patient with cardiomyopathy and hearing loss

Phenotypes of individuals with the mitochondrial A3243G mutation and amount of mutant DNA in different tissues can be very variable, but the proportio n of mutant DNA was consistantly lower in blood than muscle in previously s tudied patients. We detected the A3243G mutation in a 54-year-old patient w ith cardiomyopathy and hearing loss, where the amount of mutant DNA was hig her in blood (19%) than in muscle (16%). This shows that the level of A3243 G mutation is not always lower in rapidly dividing tissues such as blood th an in muscle, as has been presumed until now. (C) 2000 Academic Press.