Late-onset Lafora's disease with typical intraneuronal inclusions.

We describe a patient with progressive myoclonus epilepsy (late-onset Lafora's disease). Onset was in early adult life, and death was at age fifty-four. The initial symptoms were epileptic seizures and progressive dementia, with later occurrence of myoclonus. Lafora bodies were ubiquitous and in neuronal perikarya in many areas. Dust-like granular bodies predominated in the neuropil of cerebral cortex, substantia nigra, and striatum. Abnormal deposits were also found in the myocardium.