[4 cases of acquired Willebrand factor deficiency associated with monoclonal dysglobulinemia].

Acquired von Willebrand syndrome is reported in four patients with monoclonal IgG: benign gammapathy in three cases, multiple myeloma in one case; to our knowledge, this last association has not been previously reported. Coagulation abnormalities included a borderline bleeding time, a low platelet retention on glass beads, decreased levels of factor VIII coagulant activity (VIII: C), factor VIII related-antigen (VIII R: Ag) and ristocetin induced agglutination cofactor (VIII R: RC). The late clinical onset, the negative family history and the immunological abnormality suggest an acquired von Willebrand syndrome. After cryoprecipitate infusion the patients did not show the expected rise and there was no secondary increment in factor VIII: C. Time-dependent inhibition of factor VIII R: RC and factor VIII: C was found in one case only and was associated with qualitative abnormality of factor VIII R: Ag demonstrated by crossed-immunoelectrophoresis. It was not possible to interpret this last test in the other cases, due to the very low level of factor VIII R: Ag. The factor VIII abnormalities might be related to the binding and/or destruction of factor VIII by a circulating antibody, or to the adsorption of this factor on the malignant lymphocytes.