Acquired von Willebrand's disease in association with essential thrombocythemia: regression following treatment.

Acquired von Willebrand's disease in a 40-year-old woman affected with essential thrombocythemia (ET) is reported. The profile of plasma von Willebrand factor (vWF) revealed decreased ristocetin cofactor activity and diminished large multimers of vWF in spite of a normal vWF antigen level. There was no evidence of circulating inhibitor against the factor VIII complex. The vWF abnormality improved by controlling the platelet count following treatment for ET with interferon-alpha 2b and ranimustine. The possible mechanism of the development of AvWD in ET is briefly discussed.