Thrombocytopenia corrected by warfarin in antiphospholipid syndrome.

We describe a case of antiphospholipid associated thrombocytopenia in which warfarin, but not heparin, normalized the platelet count. Systemic lupus erythematosus was present in association with chorea, mitral valve stenosis, and renal thrombotic microangiopathy. No evidence of platelet consumption was detected. Low dose aspirin, pulse methylprednisolone, intravenous gammaglobulin, and cyclophosphamide also partially elevated the platelet count. Platelet activation, measured by P selectin assay, was not present during warfarin or aspirin therapy, suggesting that platelet activation may have been decreased by these treatments. We discuss possible mechanisms for correction of thrombocytopenia in antiphospholipid syndrome by warfarin.