Serum IgA deficiency induced by prolonged phenytoin treatment.

In a longitudinal study we have evaluated several immunological parameters in thirty three epileptic children and adolescents 4 to 14 years old treated with phenytoin, and matched normal controls. The patients had significantly lower levels than normal controls of IgA (153 +/- 89 vs 236 +/- 128 mg/dL p less than 0.001) and IgM (155 +/- 58 vs 217 +/- 105 mg/dL p less than 0.01). The decrease in serum IgA levels correlated with the length of treatment (r = 0.44, p less than 0.03). Eight of the patients had IgA deficiency. In 7 of these children, T lymphocytes subpopulations were determined. The results did not differ significantly from the matched controls.