Controversies in the diagnosis of Type 1 von Willebrand disease.

von Willebrand disease (VWD) is the most common bleeding disorder. Type 1 VWD represents the majority of cases and results from a partial quantitative deficiency of von Willebrand factor (VWF). The diagnosis of Type 1 VWD presents many challenges, despite there being three established diagnostic criteria: a personal history of mucocutaneous bleeding, a family history and low VWF levels. These criteria do not always coexist, and there is great overlap of clinical phenotypes and laboratory parameters between healthy individuals and those with VWD. Mild bleeding symptoms can have any number of causes and bleeding is commonly reported in the general population. VWF levels do not always correlate with bleeding symptoms and can be variable between affected family members. Additionally, VWF levels vary widely as a result of both genetic and non-genetic influences. Perhaps the greatest current controversy in the diagnosis of Type 1 VWD is that there is no consensus laboratory cut-off for the diagnosis, raising concern about both over- and under-diagnosis. Ongoing studies are addressing these issues by clarifying the underlying pathogenesis of the disease, as well as the natural history and the risk of future bleeding in those with the diagnosis.