Effect of Tamoxifen on von Willebrand Factor Levels

We read with great interest the article by Mannucci et al1 entitled "Effect of Tamoxifen on Measurements of Hemostasis in Healthy Women." We report the case of a 61-year-old woman, with blood type O, Rh positive, and von Willebrand disease (vWD) type I, who was treated with tamoxifen for breast cancer. In this case, the tamoxifen use normalized the abnormal hemostatic factors related to vWD. The patient was diagnosed as having vWD in 1991. Although the biological data ( Table ) showed a mild form of type I with normal bleeding time, 40 U/dL of von Willebrand factor (vWF) ristocetin cofactor, and 49 U/dL of factor VIII activity, the propositus was affected with a lifelong history of bleeding disorder. She experienced bleeding episodes after dental extractions, menorrhagia, post-partum hemorrhages, and in 1976, a hysterectomy was performed for menorrhagia. The mother of the propositus received blood transfusions after delivery. The patient's daughter is