[A case of MELAS associated with histochemical findings of muscles characteristic of MERRF].

We here report a 39-year-old woman of short stature with sensorineural deafness, who suddenly developed status epilepticus. T2-weighed image of brain magnetic resonance imaging (MRI) revealed a high signal lesion in the left temporal area, the distribution of which was not compatible with any particular arterial supply. Lactate and pyruvate were elevated in the serum and cerebrospinal fluid. As the mitochondrial gene analysis revealed the m.3243A>G mutation, diagnosis of mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episode (MELAS) was made. In the histochemical study of a biopsied muscle, the intramuscular blood vessels reacted strongly with SDH (SSV), but the SSV was negative for cytochrome c oxidase (COX), the findings characteristic of myoclonic epilepsy with ragged-red fibers (MERRF). This is the first case of MELAS in which the muscle histochemistry showed positive SSV unassociated with increased COX.