[Lafora's disease: diagnosis by muscle biopsy (case report)].

A 16-year-old female patient had myoclonic epilepsy caused by Lafora's disease. Muscle biopsy showed a prominent splitting pattern in muscle fibers with the nicotinamide adenine nucleotide dehydrogenase-tetrazolium reductase reaction, hematoxylin-eosin, and PAS stains. This morphologic appearance of the tissue permits diagnosis using the benign technique of muscle biopsy. The ultrastructural examination of muscle may be necessary to confirm the diagnosis of Lafora myoclonus epilepsy if light microscopical findings are equivocal.