Molecular study of VWF gene from Mexican Mestizo patients with von Willebrand disease, and the finding of three new mutations

Diagnosis of von Willebrand disease in Western Mexico

INTRODUCTION

Von Willebrand disease (VWD) is the most common inherited bleeding disorder with a prevalence of 0.1%, characterised by quantitative or functional deficiency of von Willebrand factor (VWF). VWD diagnosis is based on symptomology, biochemical and genetic tests, but limited laboratory resources and VWD heterogeneity still generate an important subdiagnosis gap worldwide and in our country.

AIM

To identify the type and subtype of VWD in a cohort of patients with a history of excessive bleeding in Western Mexico.

METHODS

This prospective cohort study from 2012 to 2019 included patients with mucocutaneous bleeding or abnormal laboratory tests. A standardised questionnaire and confirmatory tests were applied: FVIII:C, VWF activity, VWF antigen, and VWF multimeric analysis.

RESULTS

Of the 297 patients recruited, 207 (69.7%) were excluded because their values exceeded 50% in VWF activity and VWF antigen. Of those 90 remaining, 54 (18.2%) had low VWF, and only 36 patients (12.1%) were diagnosed with VWD. Among them, 17 (47.2%) had quantitative deficiencies, of whom 14 were assigned as type 1 and 3 as type 3.The remaining 19 cases were diagnosed as type 2 (52.8%): type 2A and 2B were the most frequent with 6 and 7 cases respectively; 4 cases were possible type 2M and two suggestive of 2N, however, this was not confirmed.

CONCLUSION

This study highlights the challenges of VWD diagnosis using a comprehensive panel of diagnostic tests which should extend to supplemental tests of VWF:CB, VWF:FVIIIB, and sequencing the VWD gene to confirm the results from the panel assays.

[Von Willebrand disease. Molecular biology and diagnosis]

BACKGROUND

Von Willebrand disease is the most common inherited disorder of the coagulation proteins in humans. There are three types: 1, 2A, 2B, 2N, 2M and 3. It is associated with mutations on chromosome 12 in the region p13.2, encoding the von Willebrand factor (VWF), which is synthesized in endothelial cells and megakaryocytes.

DISCUSSION

The VWF gene has been characterised using molecular biology techniques, which have acquired an important role in diagnosis von Willebrand disease, as well as in the investigation of alterations in other genes, which may be involved in regulating the synthesis, processing, and secretion of VWF. However, there are still no strategies to integrate the molecular biology diagnostic tests available. Analysis of VWF multimers is a methodology that meets the characteristics for diagnosis, but it is not easy to standardise. Considering that even in tertiary centres in our country, von Willebrand patients do not have a definitive diagnosis, it is necessary to implement these methodologies to study and improve diagnosis.

CONCLUSIONS

Von Willebrand disease is highly heterogeneous due to the molecular mechanisms that produce the various clinical and laboratory phenotypes. In Mexico there are few studies related to this disease; therefore it is essential to conduct a comprehensive study including clinical, basic, and special testing laboratory tests, in order to establish a correct diagnosis, develop new therapeutic approaches, and offer the appropriate medical care and genetic counselling.