Lafora disease: a progressive myoclonus epilepsy.

Lafora disease is a rare inborn error of metabolism resulting in storage of a polyglucosan in tissues including the brain, skin and liver. Four children are described with progressive myoclonus epilepsy and intellectual deterioration in whom this diagnosis was made. In two the diagnosis was confirmed by the presence of periodic acid schiff (PAS) positive, diastase resistant, colloidal iron staining inclusion material in the liver when they were referred to a paediatric gastroenterologist with abnormal liver function tests. In one, the diagnosis was made from cerebellar biopsy, although on retrospective review the liver biopsy performed at this time was abnormal. In a fourth child, whose sibling was affected, histological diagnosis was confirmed by skin biopsy, although clinical and EEG findings had been highly suggestive for several years. The disease has autosomal recessive inheritance, is progressive and the prognosis is poor. Paediatricians should be aware of this diagnosis, which is often delayed, as early histological diagnosis allows prognostic and genetic counselling and optimal treatment. Although the diagnosis was made by liver or brain biopsy in three cases, skin biopsy offers a reliable, less invasive means of diagnosis.