Objectifs. Au cours des gammapathies monoclonales de signification indeterminee (MGUS) ou des myelomes, les patients peuvent developper un trouble acquis de l'hemostase<space>: le syndrome de Willebrand acquis, complication rare et mal connue. Nous voulions en etudier les caracteristiques cliniques et biologiques, les hypotheses physiopathologiques et les possibilites therapeutiques. Patients. Nous avons regroupe sept observations (cinq MGUS et deux myelomes) avec une anomalie de l'hemostase repondant aux criteres classiques du syndrome de Willebrand acquis. Resultats. Le syndrome de Willebrand acquis a ete decouvert avant la gammapathie dans cinq cas sur sept. La gravite des manifestations hemorragiques depend essentiellement de l'importance du deficit en facteur Willebrand et de la presence associee d'une angiodysplasie digestive mais ne depend pas du caractere malin ou benin de la gammapathie. Le mecanisme est auto-immun<space>: un inhibiteur dirige contre le facteur Willebrand a ete trouve dans chaque observation. Le traitement du myelome a normalise l'hemostase dans un cas sur deux. Dans les MGUS, le traitement n'est indique qu'en cas d'hemorragie ou en preoperatoire. Les perfusions de concentres de facteur Willebrand ont ete peu efficaces, du fait d'une demi-vie courte. Les immunoglobulines intraveineuses ont permis une correction plus durable (trois semaines en moyenne). Elles ont ete repetees en cures regulieres dans deux cas pour des hemorragies recidivantes. Conclusion. La decouverte a un age tardif d'un deficit en facteur Willebrand justifie la recherche d'une gammapathie monoclonale. A l'inverse, devant une gammapathie, un simple bilan d'hemostase permet de depister cette complication.
Objectives. During the course of monoclonal gammopathies of undetermined significance (MGUS) or myelomas, patients could develop an acquired haemostatic disorder called acquired von Willebrand's syndrome. It's a rare and fairly unknown complication. We would like to study its clinical and biological features, its pathophysiologic hypothesis and its therapeutic possibilities. Patients and methods. Seven observations (five MGUS and two myelomas) with an haemostatic disorder responded to the classical criterias of acquired von Willebrand's syndrome. Results. Acquired von Willebrand's syndrome revealed the gammopathy in five out of seven cases. The severity of bleeding manifestations essentially depend on the importance of the deficit in von Willebrand factor and the presence associated with digestive angiodysplasia, but does not depend on the malignant or benign character of the gammopathy. The mecanism is auto-immune: an inhibitor directed against von Willebrand factor was found in each observation. The treatment for myeloma normalised the heamostas in one out of two cases. In MGUS, the treatment is only indicated in the case of bleeding or before surgery. Perfusions of concentrates of von Willebrand factor were not very efficient, due to the short half-time. Intravenous immunoglobulins permetted a longer correction (three weeks in general). They were repeated as regular treatment in two cases for recurrent bleedings. Conclusion. The detection at a later age of an abnormalities of von willebrand factor justified research of a monoclonal gammopathy. On the other hand, in case of gammopathy, a simple coagulation test allows the detection of this complication.