Atypical MELAS syndrome associated with a new mitochondrial tRNA glutaminepoint mutation

The authors studied a 47-year-old patient who presented with an association of deafness, acute cerebral stroke-like episode, leukoencephalopathy, and extensive basal ganglia calcifications. Late onset and neuroradiologic find ings were atypical for MELAS syndrome (Mitochondrial Myopathy, Encephalopat hy, Lactic Acidosis, and Strokelike episodes). A heteroplasmic G to A trans ition at nucleotide 4332 in the tRNA glutamine gene was identified in the p atient's muscle mitochondrial DNA. The pathogenicity of the mutation was sh own in single muscle fibers by the correlation between high mutation load a nd cytochrome c oxidase defect.