Drug-induced thrombocytopenia: a less known interaction.

A 57-year-old woman with a left frontal lobe tumor was started on seizure prophylaxis with phenytoin and dexamethasone while awaiting elective surgery for tumor excision. Within a week, she developed a rash all over her body secondary to phenytoin hypersensitivity and her platelet counts decreased progressively to as low as 20,000/μl. Phenytoin was discontinued and she was given intravenous immunoglobulin for 2 days. She had progressive recovery of the platelet count to her baseline over the next 6 days. This case of phenytoin-induced thrombocytopenia emphasizes the importance of recognizing thrombocytopenia secondary to drug use and also highlights a lesser known but important interaction between phenytoin and dexamethasone to enhance this effect. We also provide a brief review of the literature and comment on the pathophysiology of this rare condition.