Type 1 von Willebrand disease is extremely variable; moreover, bleeding frequently occurs in patients with it, according to study involving 482 individuals.

Investigators performed von Willebrand factor (VWF) laboratory testing and full-length VWF gene sequencing in those with von Willebrand disease and healthy controls. Among the results:

• ~Two-thirds had VWF antigen (VWF:Ag) or VWF ristocetin cofactor activity below the lower limit of normal.

• VWF sequence variations occurred in 82% of those with VWF:Ag <30 IU/dL.

• 44% of those with type 1 VWD and VWF:Ag ≥30 IU/dL had an intermediate frequency of variants.

• Those whose VWF testing was normal at baseline had a similar rate of sequence variations as controls.

• All with severe type 1 VWD and VWF:Ag ≤5 IU/dL had an abnormal bleeding score, but otherwise it did not correlate with VWF:Ag.

• Patients with a historical diagnosis of type 1 VWD had similar bleeding scores as those with low VWF levels at baseline.

Citation: Flood V, Christopherson P, Gill J, et al. Clinical and laboratory variability in a cohort of patients diagnosed with type 1 VWD in the United States. Blood. 2016;127(20):2481-2488. doi:http://dx.doi.org/10.1182/blood-2015-10-673681.