Clinical, physiological, and histological features in a kindred with the T3271C melas mutation.

The majority of patients with MELAS syndrome (mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes) have an A-->G mutation at nucleotide 3243 in mitochondrial transfer (t)RNA. To date there have only been 10 reported cases of MELAS syndrome in patients with a T-->C mutation at position 3271 of mitochondrial tRNA. Although many of the clinical features are similar between patients with these different mutations, it appears that the age at onset is later for the 3271 mutation. This report provides information from a North American kindred with the 3271 mutation (n = 6 proven; n = 2 probable; n = 3 possible) that adds clinical, physiological, histological, and molecular information to the pool of information on this rare disorder. Many of these features were similar to previous reports of both 3243 and 3271 patients. We conclude that the phenotypic expression of these different mutations are similar, but the age of onset for 3271 patients is later than for 3243 patients.