<原著>後天性von Willebrand症候群における出血機序およびその発生原因の検討

The mechanism of bleeding in acquired von Willebrand syndrome (a-vWS), which is associated with several kinds of disorders, is not established. This report investigated the pathogenesis of a-vWS associated with essential thrombocythemia (ET) and systemic lupus erythematosus (SLE). Bleeding times lengthened in 6 of 8 patients with ET; the ristocetin cofactor activity (RCof) decreased in 6 other patients, while von Willebrand factor (vWF) large multimers decreased in all patients. In three cases these abnormalities improved after platelet counts decreased following administration of busulfan. The decrease of vWF large multimers correlated with the platelet counts, but not with the plasma concentration of plasmin or elastase. In a case of SLE, plasma from an untreated period inhibited the RCof of normal plasma, suggesting that the patient plasma contained an inhibitor to vWF activity. The inhibited RCof fraction was purified with sephacryl S-300 gel filtration, DEAE sephacel column chromatography, and Mono Q column chromatography, and the molecular weight shown SDS-PAGE was about 1000kd. Electrophoresis with anti-human IgA antibody confirmed this fraction to contain IgA. The RCof activity improved with the addition of anti-human IgA antibody to the patientplasma. This study shows the possibility that anti-vWF IgA type autoantibody or the decrease ofvWF large multimers associated with the increase in platelets may cause a-vWS