Novel mitochondrial DNA ND5 mutation in a patient with clinical features of MELAS and MERRF.

BACKGROUND The mitochondrial DNA gene encoding subunit 5 of complex I (ND5) has turned out to be a hot spot for mutations associated with mitochondrial encephalomyopathy with lactic acidosis and strokelike episodes (MELAS) and various overlap syndromes. OBJECTIVE To describe a novel mutation in the ND5 gene in a young man man with an overlap syndrome of MELAS and myoclonus epilepsy with ragged-red fibers. DESIGN Case report. PATIENT A 25-year-old man had recurrent strokes, seizures, and myoclonus. His mother also had multiple strokes. A muscle biopsy specimen showed no ragged-red fibers but several strongly succinate dehydrogenase-reactive blood vessels. RESULTS Biochemical analysis showed isolated complex I deficiency and molecular analysis revealed a novel heteroplasmic mutation (G13042A) in the ND5 gene. CONCLUSIONS These data confirm that ND5 is a genetic hot spot for overlap syndromes, including MELAS and strokelike and myoclonus epilepsy with ragged-red fibers.