Hydantoin-induced cutaneous pseudolymphoma with clinical, pathologic, and immunologic aspects of Sézary syndrome.

Background: The phenytoin-induced hypersensitivity syndrome is characterized by the development of fever, rash, lymphadenopathy, and hepatitis associated with leukocytosis and eosinophilia. This article describes the unusual occurrence of a pseudo-Sézary syndrome in the days following the introduction of phenytoin treatment.

Observation: A phenytoin-induced erythroderma developed in a 60-year-old woman the histologic, cytologic, and immunologic characteristics of an erythrodermal cutaneous T-cell lymphoma of the Sézary syndrome type with lymph node involvement. The dramatic improvement after withdrawal of drug therapy and the absence of recurrence 5 years after led us to consider it as a hydantoin-induced pseudolymphoma.

Conclusions: Although lymph node pseudolymphomas induced by phenytoin are well known, few cases of hydantoin-induced mycosis fungoides have been reported in the literature. We present herein the first case of a Sézary-like syndrome associated with phenytoin therapy. Such a patient must be monitored regularly because of the risk of a true malignant lymphoma developing even many years later.