VWF and Hermansky-Pudlak syndrome: Thus despite the importance of endothelial VWF to hemostasis and the differential effects of desmopressin (DDAVP) on HPS patients (Van Dorp et al., 1990, Zatik et al., 2002, Cordova et al., 2005), how the structure and function of VWF and WPB are affected in HPS patients has not been thoroughly established.