Thrombocytopenia associated with long-term levodopa therapy.

A 63-year-old man had severe thrombocytopenia after long-term levodopa therapy. Serologic studies and clinical features indicate that the thrombocytopenia was due to an autoimmune process, presumably similar to that induced by the chemically similar drug methyldopa. Direct allergy to levodopa was ruled out by controlled challenge of the patient receiving levodopa. Combined levodopa-prednisone therapy was then instituted, with good clinical response and no recurrence of thrombocytopenia.