MELAS associated with a mutation in the valine transfer RNA gene of mitochondrial DNA

We describe a patient with the mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes (MELAS) phenotype in whom initial investigations in skeletal muscle failed to show any histochemical or biochemical defect. Subsequent analyis of the mitochondrial genome identified a new heteroplasmic mutation in the valine transfer RNA gene, the first described in this region.