Acquired von Willebrand disease is a rare condition that has been reported in post-autologous bone marrow transplant (BMT) patients, though never in post-allogeneic BMT. Here, HaemSTAR Co-lead Pip Nicolson, MA, MB BChir (Cantab), MRCP (UK), from the University of Birmingham, Birmingham, UK, describes the first ever reported case of acquired von Willebrand disease in a patient who underwent an allogeneic BMT. Speaking at the British Society for Haematology (BSH) 2018 Annual Meeting in Liverpool, UK, Dr Nicolson goes on to explain how this case study helped identify a possible link between acquired von Willebrand disease and an onset of graft-versus-host disease.