Are Iranian patients with von Willebrand disease type 2N properly differentiated from hemophilia A and do they receive appropriate treatment?

Application of genetic testing for the diagnosis of von Willebrand disease

von Willebrand disease (VWD) is the most frequent inherited bleeding disorder, with an estimated symptomatic prevalence of 1 per 1000 in the general population. VWD is characterized by defects in the quantity, quality, or multimeric structure of von Willebrand factor (VWF), a glycoprotein being hemostatically essential in circulation. VWD is classified into 3 principal types: low VWF/type 1 with partial quantitative deficiency of VWF, type 3 with virtual absence of VWF, and type 2 with functional abnormalities of VWF, being classified as 2A, 2B, 2M, and 2N. A new VWD type has been officially recognized by the ISTH SSC on von Willebrand factor which has also been discussed by the joint ASH/ISTH/NHF/WFH 2021 guidelines (ie, type 1C), indicating patients with quantitative deficiency due to an enhanced VWF clearance. With the advent of next-generation sequencing technologies, the process of genetic diagnosis has substantially changed and improved accuracy. Therefore, nowadays, patients with type 3 and severe type 1 VWD can benefit from genetic testing as much as type 2 VWD. Specifically, genetic testing can be used to confirm or differentiate a VWD diagnosis, as well as to provide genetic counseling. The focus of this manuscript is to discuss the current knowledge on VWD molecular pathophysiology and the application of genetic testing for VWD diagnosis.

Diagnostic Challenges in Children With Congenital Bleeding Disorders: A Developing Country Perspective

OBJECTIVES

To assess the frequency and characteristics of children with inherited bleeding disorders that were initially misdiagnosed, leading to inappropriate disease management.

METHODS

This study was conducted at the Haematology/Pathology Department of Fauji Foundation Hospital, Rawalpindi, Pakistan, from August 2014 to August 2018. Children who were diagnosed with an inherited bleeding disorder but did not respond to initial therapy were reevaluated.

RESULTS

In total, 62 children were diagnosed with a bleeding disorder. Of these, 27 were diagnosed with an inherited bleeding disorder and 35 with an acquired bleeding disorder. Of the 27 children with inherited bleeding disorders, 18% (n = 5) were misdiagnosed and treated inappropriately. The median age of the misdiagnosed patients was 9 years (range, 5-13 years). Three patients with Bernard-Soulier syndrome had been misdiagnosed as having immune thrombocytopenic purpura, 1 patient with von Willebrand disease had been misdiagnosed as having hemophilia A, and 1 patient with haemophilia B had been misdiagnosed as having hemophilia A.

CONCLUSIONS

There are chances of misdiagnosis and improper or invasive management if comprehensive laboratory evaluation and a thorough clinical evaluation are not performed in children with congenital bleeding disorders.

Von Willebrand disease type 2N: An update

Quantitative or qualitative defects of von Willebrand factor (VWF) are responsible for the most common inherited bleeding disorder, von Willebrand disease (VWD). Type 2N VWD is an uncommon recessive disorder that results from gene mutations located in the region coding for the binding site of VWF for factor VIII (FVIII). This narrative review describes the pathophysiology, diagnostic procedures and treatment as well as the molecular biology of type 2N VWD. Although other VWF-dependent functions like binding to platelets and collagen are preserved, FVIII plasma levels are low due to the rapid clearance of this moiety in the absence or reduction of its binding to VWF. The diagnosis of type 2N should be considered in patients with low FVIII coagulant activity (FVIII:C) and disproportionally higher VWF antigen, especially when they present with an autosomal recessive pattern of inheritance. Because an accurate diagnosis is essential for genetic counseling and optimal treatment, type 2N must be distinguished from mild/moderate hemophilia A and its carrier state. This differential diagnosis can be obtained by using the laboratory assay of the FVIII binding capacity of VWF (VWF:FVIIIB) or analysis of the FVIII binding site on the VWF gene.