IgA deficiency, epilepsy, and hydantoin medication.

Serum-immunoglobulin concentrations were measured in 364 patients with epilepsy. On dividing the patients into those treated with or without hydantoins, and according to possible aetiological factors, a characteristic pattern emerged. Irrespective of the treatment given, the mean values of IgA were significantly reduced in patients in whom constitutional factors were apparent, including those with familial prevalence of seizures. While IgA was rarely found below 0-6 mg/ml, a limit chosen to define IgA deficiency in patients not treated with hydantoins, the IgA level was subnormal in 20-25% of the patients treated with such drugs. In contrast, the mean concentration of IgA was normal and no individual subnormal values were observed in epileptic patients treated with or without hydantoins whose disease was thought to be secondary to traumatic or infectious events or to metabolic disturbances. The data suggest that epilepsy with constitutional characteristics might predispose to low IgA, but that IgA deficiency only occurs when hydantoins are given. Whether this postulated predisposition is relevant to the aetiology or pathogenesis of epilepsy remained unresolved.