A Compound Heterozygosis of Two Novel Mutations in vWF Exacerbates vWD in a Chinese Pedigree.

Abstract

von Willebrand disease (vWD), caused by mutations in the von Willebrand factor (vWF) coding gene, is a disease characterized by abnormal coagulation activity and a severe tendency for hemorrhage. Therefore, identifying mutations in vWF is important for diagnosing congenital vWD. We studied a 23-year-old male vWD patient and his parents. Clotting methods were used to determine activated partial thromboplastin time (aPTT), prothrombin time (PT), fibrinogen (FIB) levels, FVIII activity. Chromogenic substrate method was used to determine vWF antigen and activity. The platelet count was determined. Mutations were searched using whole-exome sequencing and certified by Sanger sequencing. Clinical data, including activated partial thromboplastin time (APTT), prothrombin time (PT), thrombin time (TT), fibrinogen levels, FX activity, FX antigen levels, and the platelet count were collected. A mixing study was performed to eliminate the presence of coagulation factor inhibitors and lupus anticoagulants. Mutations were screened by using whole-exome sequencing (WES) and were verified by using Sanger sequencing. The proband showed severely decreased vWF antigen, vWF activity, and FVIII activity. RIPA (RISTO-CETIN-induced platelet aggregation) was 0%. Data from WES showed that the proband carried compound heterozygous variants vWF: NM_000552.5 (c.3213C>A p.Cys1071Ter) and vWF: NM_000552.5 (c.6598+2T>C). The proband's mother carried variant vWF: NM_000552.5 (c.3213C>A p.Cys1071Ter) while the proband's father carried variant vWF: NM_000552.5 (c.6598+2T>C). All laboratory test indexes of the proband's parents, including vWF antigen, vWF activity, and FVIII activity, were within the normal ranges. We identified a compound heterozygosis with two novel mutations in vWF (c.3213C>A, c.6598+2T >C) in a family pedigree, and our results demonstrate that the compound heterozygous mutations probably exacerbate vWD.