Successful treatment of a young infant who developed high-titer inhibitors against VWF-cleaving protease (ADAMTS-13): Important discrimination from Upshaw-Schulman syndrome

We report herein the case of a 9-month-old female infant with acquired thrombotic thrombocytopenic purpura (TTP), which was initially suspected to be either Upshaw-Schulman syndrome (USS or a congenital TTP) or hemolytic uremic syndrome (HUS) because of onset of clinical signs in infancy and accompanying diarrhea. She received combination therapy of plasma exchange, steroid pulse, and high-dose intravenous immunoglobulin infusion that was initiated before the definitive diagnosis, which resulted in excellent clinical improvement. The retrograde analysis of plasma ADAMTS-13 activity and its inhibitor showed a lack of this enzyme activity and the presence of a high-titer IgG inhibitor (200-320 Bethesda units/mL) to this enzyme activity. From our experience, it was suggested that we should recognize the possibility of the patient with acquired TTP in infancy and the importance of plasma exchange therapy for management of its clinical symptoms.