The first description of microparticles dates back to 1967, when Wolf reported platelet membrane fragments in human plasma

Patients with acute leukemia develop abnormalities of haemostasis, leading not only to bleeding, but also to thrombotic complications. The pathogenesis of these complications is complex and multifactorial. Because plate-

Acquired von Willebrand disease (AvWD) represents a rare, potentially severe and most likely underdiagnosed category of hemorrhagic syndromes determined by quantitative, qualitative or functional, nonhereditary, alterations of von Willebrand factor (vWF) that occur in the context of various underlying diseases. It is diagnosed mainly in adults, without any personal or familial history of bleeding. The etiopathogeny of AvWD is complex, marked by the intervention of multiple mechanisms, occuring in the evolution of neoplasia, autoimmune disorders, cardiovascular diseases and other conditions. The clinical and laboratory manifestations are similar to the congenital form with mucocutaneous hemorrhage in patients without bleeding history and demonstration of quantitative and/or functional anomalies of vWF. Treatment has two major objectives: control of bleeding and therapy of the underlying condition. As a practical illustration of the theoretical aspects we present 3 clinical cases of AvWD diagnosed in the Colţea Hospital Department of Hematology during the last 10 years.