Impact of 789Ala/Ala genotype on quantitative type of von Willebrand disease.

von Willebrand factor (VWF) is a complex multimeric plasma glycoprotein encoded by an approximately 178-kb large VWF gene located on the short arm of chromosome 12 (12p13.2). VWF plays an important role in hemostasis through binding with platelet GpIbalpha receptors. We made an attempt to correlate the 789Ala/Ala genotype of the VWF with VWF:Ag level in different types of unrelated von Willebrand disease (VWD) patients and healthy controls. VWF assays and other coagulation screening tests have been done for all 103 (50 male, 53 female) different types of index VWD patients including 19 type 1, 55 type 2, and 29 type 3 VWD patients. Genotypes were detected by polymerase chain reactions followed by restriction fragment length polymorphism. The genotype 789Ala/Ala was found in 26.3% type 1 and in 31.0% type 3 patients. This genotype was not found in any of type 2 patient or healthy controls. Overall, 789Ala/Ala genotype was found significantly higher (P < 0.001) in quantitative type (type 1 and type 3) VWD that is occurred due to low VWF:Ag level. These results demonstrate that mutant homozygous 789Ala/Ala genotype of this polymorphism probably have their functional implications for low plasma VWF:Ag level in quantitative type of VWD.