Roles of protein C, protein S, and antithrombin III in acute leukemia.

Protein C, protein S, and antithrombin III were measured in 35 patients with acute leukemia (13 with AML and 22 with ALL). Low levels of proteins C and S were present in 15 (42.9%) and 20 (57.1%) patients, respectively, and 6 patients had low levels of antithrombin (ATIII). Seven patients also had DIC at presentation. There were no significant differences in the levels of protein C, protein S, and ATIII in patients with or without DIC. Twenty patients were available for re-evaluation at the end of induction therapy. The low levels of protein C and ATIII found at diagnosis had risen to normal levels at the end of the induction therapy, while low =levels of protein S remained in 75% of the patients. One patient with low protein C at presentation developed myocardial infarction on day 15, and another patient died of progressive neuropathy. No other thrombotic manifestations were seen. Whether the low protein C, protein S, or antithrombin levels predispose patients with acute leukemia to thrombosis in the absence of DIC is not known.