Potential danger of thrombosis after plasma exchange in the treatment of patients with immune disease.

Coagulation studies were serially performed before and after repeated plasma exchange in seven patients with myashtenia gravis. The fall in platelets and coagulation factor activities after plasmapheresis using a replacement material devoid of clotting factors was not so low that bleeding episodes were to be feared and no hemorrhages were observed. In contrast, thrombotic phenomena were suspected in two patients. Antithrombin III fell to undetectable levels in some cases. This finding associated with elevated values of factor VIII related antigen, factor VIII coagulant activity and von Willebrand factor suggested a potential danger of thrombosis in such treated patients.