Myoclonic seizures in Krabbe disease: a unique presentation in late-onset type.

Krabbe disease is a rare, recessively inherited degenerative disorder of myelin, caused by a deficiency of the lysosomal enzyme galactocerebroside beta-galactosidase. Ninety-five percent of cases begin in early infancy, typically presenting with irritability, hypertonicity, tonic spasms, visual loss with optic atrophy, and occasionally seizures. In 5% of cases, symptoms begin late, between 15 months and 10 years, usually presenting with spastic paralyses, cerebellar ataxia, visual failure, and peripheral neuropathy. Seizures occasionally develop months to years after symptom onset. In a review of 50 such cases from the world literature, in only two did seizures signal the onset. This report describes an 18-month-old male with late-onset Krabbe disease who is the first such reported patient presenting with myoclonic seizures, an epileptic encephalopathy normally thought to reflect gray matter disease.