Thirdly, the endothelial contribution to haemostasis is not displayed in VHA and therefore, conditions affecting the endothelium such as von Willebrand disease (vWD, quantitative or qualitative defects in vWF and, hence inability of the platelets to adhere to the endothelium), cannot be investigated. This evidence concerns the gene VWF and von Willebrand disease (hereditary or acquired).