Erythroderma, hypogammaglobulinemia, and T-cell lymphocytosis. Occurrence following therapy with phenytoin.

Erythroderma and exfoliative dermatitis developed in a 17-year-old boy following therapy with phenytoin sodium. Immunologic studies performed early in the course of the dermatitis disclosed panhypogammaglobulinemia and a marked increase in T lymphocytes that responded poorly in vitro to T-cell mitogens. After therapy with prednisone, the dermatitis improved somewhat, and the patient's lymphocytes proliferated in vitro when exposed to phenytoin. We speculate that our patient's acute hypersensitivity reaction may have been mediated by an excessive number of phenytoin-sensitized suppressor-cytotoxic T lymphocytes and may represent a disorder of immunoregulatory T cells.