Recurrent venous thrombosis in a patient with chronic lymphocytic leukemia and acquired protein S deficiency.

A patient with chronic lymphocytic leukemia and an undetectable plasma level of protein S (PS), associated with recurrent venous thrombosis, is described. The laboratory investigation revealed the concomitant presence of an inhibitor directed to PS and a monoclonal protein in the patient's plasma. After treatment with prednisone and cyclophosphamide both the inhibitor to PS and the monoclonal component disappeared.