SUMMARY
Introduction: Acquired von Willebrand syndrome (AVWS) is an underestimated bleeding disorder characterised by either a shortage or dysfunctional von Willebrand factor (VWF) and mostly associated with several cardiac, autoimmune and hematologic disorders, including myeloproliferative neoplasms (MPNs).
Case series: We describe three patients with MPN (i.e., two with essential thrombocytosis and one with secondary myelofibrosis from polycythaemia vera) of which one experienced unexpected bleeding after bone marrow puncture. Laboratory investigation showed normal-to-high VWF:Ag levels with a disproportional decrease in VWF activity in all three patients. These results represent a qualitative VWF defect due to secondary AVWS.
Conclusion: Although thrombotic events are a frequent complication found in MPN patients, unexplained and potentially severe bleedings are a not uncommon observation. In the latter situation, AVWS should always be excluded, minimally by determination of VWF:Ag and VWF activity (e.g., VWF:RCo and VWF:CB). MPN-patients with AVWS may benefit from additional prevention against bleeding.
(BELG J HEMATOL 2025;16(3):130–4)
