Type 2B von Willebrand Disease: An Unusual Cause of Severe Neonatal Thrombocytopenia.

An infant with presumed maternal immune thrombocytopenic purpura had persistent thrombocytopenia with platelet clumping. The patient had no significant bleeding symptoms in the first year of life and von Willebrand antigen and ristocetin cofactor activity were normal. Absent high molecular weight multimers ultimately led to a genetically proven diagnosis of type 2B von Willebrand disease (3964G>A VWF exon 28), highlighting the challenges of establishing this diagnosis in infants.