A patient on chronic phenytoin (Dilantin) therapy may develop a benign lymphoproliferative disorder called pseudolymphoma. A patient on chronic phenytoin therapy is also at increased risk for true lymphoma (see next section).
Most patients have been taking phenytoin for months or years, but occasionally the syndrome may develop after only a few weeks.
Clinical features:
(1) fever
(2) arthralgias
(3) cutaneous rash
(4) hepatosplenomegaly
(5) eosinophilia
(6) lymph node enlargement
Pathologic features:
(1) atypical lymphoid proliferation without the changes of Hodgkin's disease
(2) absence of molecular indicators of malignancy (polyclonal lymphocytes with no clonal lymphoid population)
The lymphadenopathy and clinical findings revert within a few weeks if the phenytoin therapy is stopped.
Some patients may show improvement after discontinuation of phenytoin therapy only to develop a true lymphoma later. Because of this risk the patient should have careful follow-up.
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