Pathogenic mutations of the human mitochondrial genome are associated with well-characterized, progressive neurological syndromes, with mutations in the transfer RNA genes being particularly prominent.
To describe a novel mitochondrial transfer RNAPro gene mutation in a woman with a myoclonic epilepsy with ragged-red fibers–like disease.
Design, Setting, and Patient
Case report of a 49-year-old woman presenting with a myoclonic epilepsy with ragged-red fibers–like disease comprising myoclonic jerks, cerebellar ataxia, and proximal muscle weakness.
Histochemical analysis of a muscle biopsy revealed numerous cytochrome-c oxidase–deficient, ragged-red fibers, while biochemical studies indicated decreased activity of respiratory chain complex I. Molecular investigation of mitochondrial DNA revealed a new heteroplasmic mutation in the TψC stem of the mitochondrial transfer RNAPro gene that segregated with cytochrome-c oxidase deficiency in single muscle fibers.
Our case serves to illustrate the ever-evolving phenotypic spectrum of mitochondrial DNA disease and the importance of performing comprehensive mitochondrial genetic studies in the absence of common mitochondrial DNA mutations.