A novel mutation in the mitochondrial DNA transfer ribonucleic acidAsp gene in a child with myoclonic epilepsy and psychomotor regression.

A novel A7543G mutation was found in the mitochondrial DNA transfer ribonucleic acidAsp gene in an 11-year-old girl with myoclonic seizures, developmental delay, and severe behavioral problems. Muscle histochemistry failed to show any ragged red fibers or cytochrome c oxidase-negative fibers, and muscle biochemistry showed partial cytochrome c oxidase deficiency. The mutation was heteroplasmic in muscle, fibroblasts, and blood from the patient and in blood from other affected family members, and the proportion of mutant mitochondrial DNA correlated with the severity of symptoms.