Classification of von Willebrand disease: emerging issues

Area of Science:

• Hematology
• Genetics
• Clinical Medicine

Background:

• Von Willebrand disease (vWD) is classified into three main types: Type 1 (quantitative deficiency), Type 2 (qualitative abnormalities), and Type 3 (near-total absence).
• The molecular genetic basis for Type 1 vWD remains largely elusive, unlike Types 2 and 3.
• Type 1 is considered the most prevalent form of vWD.

Purpose of the Study:

• To investigate the molecular genetic background of patients previously diagnosed with Type 1 vWD.
• To evaluate the clinical and laboratory characteristics of these patients.
• To assess the utility of the current vWD classification system.

Main Methods:

• Retrospective analysis of patients diagnosed with Type 1 vWD.
• Identification of specific mutations (R611C and R552C) previously classified as Type 2.
• Comparison of laboratory findings and response to DDAVP (1-deamino-8-D-arginine vasopressin) in affected patients.

Main Results:

• Approximately 25% of patients diagnosed with Type 1 vWD were found to carry mutations (R611C or R552C) recently designated as Type 2.
• These patients exhibited laboratory characteristics and responded well to DDAVP, similar to Type 1 vWD.
• The identified mutations likely cause minor, clinically insignificant functional deficiencies in heterozygous form.

Conclusions:

• The current classification of vWD may not accurately distinguish between certain quantitative and qualitative defects.
• Mutations R611C and R552C present a diagnostic challenge, blurring the lines between Type 1 and Type 2 vWD.
• Re-evaluation of the vWD classification is warranted based on these findings.