Hereditary spastic paraplegia with epileptic myoclonus.

A previously undescribed form of complicated hereditary spastic paraplegia with epileptic myoclonus in four affected offspring of consanguineous parents is reported. The disorder was inherited as an autosomal recessive trait. Age at onset varied from the prenatal period to 10 years. The main findings when examined between 26 and 42 years of age were spastic paraplegia, epileptic myoclonus, distal muscle atrophy, mental retardation or dullness, ataxia, hearing loss and a progressive course. The difference in phenotypic expression was striking. One woman had progressive epileptic myoclonus, ataxia and only slight distal wasting and could have been misdiagnosed as a case of Unverricht-Lundborg's disease. Thorough biochemical investigations revealed no cause of the disorder.