Chronic diphenyl hydantoin encephalopathy in mentally retarded children and adolescent with severe epilepsy.

An account is given of chronic diphenyl hydantion (DPH) encephalopathy in 21 mentally retarded epileptics with increasing psychomotor deterioration, choreiform hyperkinesia, deposits of immunoglobulins in the skin, and changes in serum immunoglobulins. Three months after withdrawal of DPH the condition proved partially reversible, from the clinical as well as laboratory point of view. Eleven patients have been followed for 1 year after discontinuation of DPH, and the findings were largely unchanged from the 3-month follow-up examination. Before the drug was withdrawn, seven patients exhibited deposits of immunoglobulins at the dermo-epidermal junction and in vessel walls. At the end of 1 year such deposits were found in only three patients, all of whom were on another antiepileptic drug.