Transient neonatal acquired von Willebrand syndrome due to transplacental transfer of maternal monoclonal antibodies.

Although typically a disorder of adults, acquired von Willebrand syndrome (AVWS) is increasingly being recognized in the pediatric population in association with congenital cardiac diseases, certain neoplasia, and hypothyroidism. Transplacental transfer of maternal immunoglobulin G (IgG) antibodies as a cause of neonatal disorders in infants born to mothers with autoimmune conditions has been reported. We describe the diagnosis and peripartum clinical management of AVWS due to monoclonal gammopathy of undetermined significance (MGUS) and the first reported case of transient neonatal AVWS due to transplacental transfer of maternal IgG antibodies.