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Expression of GpIb on plasma cells in a patient with monoclonal IgG and acquired von Willebrand disease

Summary. To get insights into the pathogenesis of acquired von Willebrand disease associated with plasma cell dyspasias, we searched for the expression of the physiological von Willebrand factor receptor, the GpIb/GpIX complex, on bone marrow plasma cells. The monoclonal spike in our patient corresponded to IgGκ molecules; there was no plasma inhibitor to vWF:Ag or vWF:RiCoF. The bone marrow contained 1–2% plasma cells. Fresh bone marrow cells or plasma cells enriched bone marrow cells after a 48 h in vitro culture in the presence of interleukin 6 were stained by an immuno alkaline phosphatase technique using monoclonal antibodies (mAb) to von Willebrand factor, GpIb α and β chain, GpIIb/IIIa and Gp IX. Two different mAb to GpIb α chains reacted with the majority (75%) of plasma cells whereas all other reagents yielded no staining. Malignant plasma cells from patients with multiple myeloma without haemostatic disorder were unreactive with anti‐GpIb mAb. These data suggest that in some patients with acquired von Willebrand syndrome there is a GpIb mediated selective adsorption of von Willebrand factor on clonal plasma cells.