IgG kappa monoclonal gammopathy of undetermined significance presenting as acquired type III Von Willebrand syndrome.

Acquired von Willebrand syndrome (AVWS) is a rare bleeding disorder associated with hematoproliferative disorders, autoimmune conditions, neoplasia and cardiovascular disorders that often present a diagnostic challenge. Monoclonal gammopathy of undetermined significance (MGUS) is one of the most common causes of AVWS that typically presents later in life with mucocutaneous or postsurgical bleeding and multimers consistent with type I or II von Willebrand disease (VWD). Here, we present the case of a patient with a 32-year history of type III VWD that was ultimately found to be AVWS related to an IgG MGUS. In this case report, we highlight the diagnostic challenges of AVWS to ensure proper identification and potentially lifesaving treatment of this rare disorder.