Erythroderma and marked atypical lymphocytosis mimicking cutaneous T-cell lymphoma probably caused by phenobarbital.

A 56-year-old man had been treated with phenobarbital seven weeks prior to admission. One month after initiation of administration of phenobarbital, fever, skin rash and lymphadenopathy occurred. Nine days later, marked atypical lymphocytosis, eosinophilia and hepatic injury was noticed. The histology of the biopsied skin was indistinguishable from lymphoma. CHOP-therapy was started but the patient was followed without further treatment because of polyclonal T-lymphocytosis. Afterward, clinical and hematologic improvement ensued and he has been well until now, 52 months later. The marked T-lymphocytosis observed in this case is probably a lymphoid leukemoid reaction secondary to hypersensitivity to phenobarbital.