Thrombosis in VonWillebrand disease.

Objective: To date, only a few case studies have reported occurrence of thrombosis in patients with VonWillebrand disease (VWD). No studies have looked at its incidence in this patient population. The aim of this study was to test our hypothesis that decreased VonWillebrand factor (VWF) levels confer a protective effect on arterial and venous thrombosis.

Methods: This is a retrospective cohort study including patients (n=350) with the ICD-9 code of VWD who were identified from our hospital database over a period of 25 years, out of which 198 patients were included in the final sample. A parallel control sample without VWD matched for age, sex, hypertension, hyperlipidemia, atrial fibrillation and diabetes mellitus was also obtained from the hospital database. The primary outcomes were incidence of diagnosis of symptomatic arterial and venous thrombosis. The results were computed using multivariate conditional logistic regression analysis and proportions were compared using McNemer's Chi - square test.

Results: Out of 198 patients (mean age 44.2 ± 17.5, women 72%) with VWD, 170 (86%) were VWD type 1, 21 (10%) were type 2 and 7 (3%) were type 3. VWD was found to be an independent protective predictor from arterial thrombosis (OR 0.28, 95% CI 0.14-0.54, p<0.0001), more so in CAD (OR 0.28, 95% CI 0.12-0.64, p=0.002) than in CVD (OR 0.28, 95% CI 0.10-0.77, p=0.01). However this was not the case in venous thrombosis (p=0.42).

Conclusion: In a population of relatively younger individuals with VWD, our study suggests a reduced incidence of arterial thrombosis but not of venous thrombosis. This brings up the possibility that there could be other pathways or factors involved in arterial and venous thrombosis. To our knowledge, this is the first large observational study that has provided insight into the thrombotic disease in this group of patients.