Clinical course of a patient with USS (no. 16) and schematic illustration how a USS newborn with a PDA develops hemolytic jaundice and thrombocytopenia during the newborn period. (A) First episode (indicated by ①: She was born at full-term and weighed 3018 g. Nineteen hours after birth, she developed severe hemolytic jaundice and thrombocytopenia (patient no.16 in Table 1). She underwent exchange blood transfusions 4 times within the first 2 days of life. Then, she gradually developed generalized edema, and on day 8, the comorbidity of a PDA (3.8 mm in diameter) was diagnosed. Second episode (indicated by ②: On day 11, the patient developed cyanosis as a result of left cardiac failure followed by hemolysis and thrombocytopenia, so she received oxygen therapy under intubation. Third episode (indicated by ③: After clinical improvement, on days 19 to 21 she underwent intravenous administration of indomethacin with the intention of supporting PDA closure. This treatment was ineffective, and her clinical condition worsened with recurring hemolysis and thrombocytopenia on day 26. Surgical ligation of the PDA: On day 29, she underwent surgical ligation of the PDA. Thereafter, the clinical signs of hemolysis and thrombocytopenia ceased until she was 14 months old, when she had chickenpox. (B) Schematic illustration shows how a newborn with USS who has a PDA develops severe and recurring episodes of hemolytic jaundice and thrombocytopenia during the newborn period. Note that a newborn with normal ADAMTS13 activity and persisting PDA often develops acquired von Willebrand syndrome.^19,20  BUN, blood urea nitrogen; LDH, lactate dehydrogenase; UL-VWFMs, unusually large VWF multimers.