A rare case of type 2A von Willebrand disease with compound heterozygous mutation

A 27-year-old woman presented to our hematological department with gingival bleeding for two days after tooth extraction. She denied a familial history. Her previous history included frequent epistaxis and once heavy menorrhagia in 2007 treated with plasma transfusion. She underwent laparoscopic surgery for luteal rupture, but there was no remarkable increase in bleeding.

On admission, the systemic physical examination revealed unremarkable. No active bleeding symptoms were found. Complete blood count was normal (Table 1). Coagulation tests including prothrombin time, fibrinogen, activated partial thromboplastin time and thrombin time were within normal ranges (Table 1). But platelet aggregation function suggested impaired AA (Arachidonic acid) induced-aggregation, with maximal aggregation rate of 14.3%. Low concentration of ristocetin induced decreased platelet aggregation while high concentration of ristocetin induced normal aggregation. Coagulation factor test revealed a FVIII activity of 43% and a VWF antigen level of 26.2% (Table 2). VWF multimeric assay (Fig. 1) showed a remarkable decrease of HMWM (high molecular weight molecule) and IMWM (medium molecular weight molecule). The whole-exome sequencing demonstrated the existence of compound heterozygous mutations in the VWF gene, in which a c.2281 + 1G > A heterozygous mutation from her father and a c.4654T > A (p.Phe1152Ile) heterozygous mutation from her mother (Fig. 2 ). Based on all above results, the diagnosis of type 2A VWD was confirmed, according to the VWD diagnosis criteria [14].

In this article, we report a rare case of hereditary VWD of type 2A in a female patient with compound heterozygous mutation in VWF gene. She presented with gum bleeding after tooth extraction. On laboratory examination, her platelet count and routine coagulation tests were normal. but VWF: Ag and VWF: Ac were significantly lower than normal while FVIII activity was slightly reduced. Laboratory investigations indicated that FVIII:C was 43%, VWF: Ag was 26.2%, and VWF: Ac was 5.7%, VWF: Ac/VWF: Ag was < 0.7, which excluded VWD 1C, 2N, and 3. RIPA (Ristocetin-induced Platelet Aggregation) test was negative for high platelet affinity which excluded VWD type 2B. Moreover, VWF multimer assay demonstrated HMWM deletion and IMWM reduction, which excluded type 2M. Therefore, the patient was confirmed as VWD type 2A. For the father of this patient, VWD diagnosis was not made because both of his VWF: Ag and VWF: Ac were more than 50%, in accordance with the recommendations for the laboratory diagnosis of VWD [12, 15].His genetic mutation has not been reported in VWD patients. The British Committee for Standards in Haematology recommends that patients should be diagnosed with “low VWF” if their VWF: Ag level of 30–50% [16]. Her mother’s VWF: Ag level was 40% and thus she was diagnosed as low VWF.

The International Society on Thrombosis and Haemostasis (ISTH) bleeding assessment tool (BAT) is employed for patients with von Willebrand disease (VWD) [17]. The patient was evaluated with a score of 7 based on the ISTH-BAT, frequent epistaxis (score 1), bleeding after tooth extraction (score 2), and heavy menorrhagia with plasma transfusion (score 4).

To further investigate the patient’s VWD pathogenesis, whole-exome sequencing and one-generation sequencing validation were performed on the patient. The results showed that both the patient and her father had a heterozygous mutation in intron 17 of the coding region of the VWF gene, c.2281 + 1G > A, which is an intronic shear mutation and the peptide chain is located between the D2 and D’ structural domains of the preceding peptides of the VWF gene. Genetic sequencing also revealed that both the proband and her mother had a heterozygous mutation in exon 28 of the coding region of the VWF gene, c.4654T > A (p.Phe1152Ile), which is a missense mutation located in the A2 region of the VWF maturation subunit. A search through gene databases did not reveal either of these genes and they have not been reported in the national or international literature. According to the ACMG guidelines, her father’s c.2281 + 1G > A gene is a pathogenic variant, while her mother’s c.4654T > A (p.Phe1552Ile) is a variant of unknown clinical significance. The two VWF alleles mutations are inherited from each parent. While coexistence of one defective and one normal gene, there are no significant clinical symptoms due to the presence of the normal dominant gene. When the offspring received each of the two defective VWF genes, they presented a clinical phenotype. Therefore, neither of the patient’s parents had a history of abnormal bleeding, but this patient presented with abnormal bleeding due to compound heterozygous mutation. Literature reported that gene mutation in type 2A VWD is often located in the A1-A2, D1-D3 and CK region, of which 82% is located in the A1-A2 region, about 8% is related to the D2 region, CK region, and there is also 1% in the D3 region. 73% of the mutation in the type 2 A VWF gene is located in exon 28, missense mutation accounted for 90%.

In recent years, more and more researchers have paid attention to VWD, and significant progress has been made in understanding the molecular pathogenesis of VWD, which has improved the diagnostic and therapeutic strategies for VWD. VWD-related investigations including VWF: Ag detection, VWF: Ac, DDAVP test, VWF gene sequencing, and multimer assay have improved the accuracy of diagnosis of VWD, but few hospitals in China routinely perform them. Therefore, diagnosis and proper management of VWD remain difficult and challenging. Currently, treatments for VWD include exogenous VWF factor supplementation and antifibrinolytic drugs. Desmopressin is contraindicated in patients with type 2B VWD due to increased binding of VWF to platelets, which exacerbates thrombocytopenia [18]. At present, no VWF concentrate product is available and recombinant human VWF is still in pre-clinical stage. Thus, a large amount of work should be done to improve the diagnosis and treatment for VWD patients in China.