[Hemostasis disorders with reduced activity of the von Willebrand factor in myeloproliferative syndromes].

Splenectomy performed in a patient with polycythaemia vera and incipient osteomyelofibrosis was complicated by severe postoperative bleeding. A transient decrease of factor VIII/von Willebrand factor (VIIIR:WF) was detected as a possible cause of the bleeding tendency. As a result of this observation the VIIIR:WF system was investigated in all patients with myeloproliferative disorders who are presently followed by this laboratory. Subnormal VIIIR:WF activity was found in 5 of 9 prospectively investigated patients with polycythaemia vera and in one of 12 patients with chronic myeloid leukemia. These results suggest that acquired defects of the VIIIR:WF system are, in addition to the well known functional abnormalities of blood platelets, quite common in myeloproliferative disorders, especially polycythaemia vera, and must be reckoned with before surgery in particular. When specific antibodies directed against VIIIR:WF have been ruled out, the etiology of the VIIIR:WF defect found in our patients remains unclear.