VWF and von Willebrand disease 3: von Willebrand disease (VWD) is often caused by genetic defects in the von Willebrand factor (VWF) gene and is divided into three major subtypes: type 3 (VWD3) is characterized by total absence of VWF, type 2 (VWD2) by functional disturbance of VWF, and type 1 (VWD1) by low plasma concentration of functionally normal VWF.1Diagnosis of VWD is challenging due to the heterogeneity of the disease and can be made based on phenotypic testing alone; therefore, mutation analysis has not been regarded as necessary.2