The normal distribution of von Willebrand factor (VWF) levels is wide. Low levels are associated with bleeding symptoms and von Willebrand disease (VWD). We have recently described a high prevalence of bleeding symptoms in a whole age group of young females (n = 1,019) from Malmo, Sweden. It was the objective of the present study to evaluate the distribution of VWF levels in young females with or without bleeding symptoms in this population, and the influence of ABO blood group and promoter haplotypes on VWF levels and to identify a possible increased prevalence of VWD in females with bleeding symptoms. A random selection of the female age group (n = 246), into a study group (n = 176) with, and a control group (n = 70) without bleeding symptoms, was evaluated. Eighteen girls had VWF:RCo below the reference range, of which 17 belonged to the study group (17/176, 9.7%), and one to the control group (1/70, 1.4%) (p = 0.017). Blood group O was found in 14/18 girls with low VWF:RCo. There was a highly significant correlation between VWF:RCo and blood group O and non-O genotypes. Two common VWF promoter haplotypes did not contribute to the VWF:RCo variation. VWF levels did not correlate with time during menstrual cycle, or the use of oral contraceptives. No case fulfilled the diagnostic criteria for VWD. In conclusion, low VWF:RCo was significantly more frequent in females with bleeding symptoms. However, we found no case fulfilling strict diagnostic criteria for VWD. The ABO blood group was a strong modifier, but VWF promoter haplotypes had no association to VWF levels in this population.
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