Thrombocytopenia in a 7-day-old Male.

1. Lindy Zhang, MD*,† 2. Caroline DeBoer, MD†† 3. Alejandra Ellison-Barnes, MD‡ 4. Jessica Berger, MD‡‡ 5. Courtney E. Lawrence, MD*,¶ 6. Rosalyn W. Stewart, MD MS MBA‡,§ 7. Lydia H. Pecker, MD** 1. *Departments of Pediatric Hematology, 2. †Pediatric Oncology, 3. ‡Internal Medicine, and 4. §Pediatrics and 5. ¶Division of Transfusion Medicine, Department of Pathology, and 6. **Division of Hematology, Department of Medicine, Johns Hopkins School of Medicine, Baltimore, MD; 7. ††Advocate Aurora Healthcare, Milwaukee WI; 8. ‡‡Department of Anesthesiology and Critical Care Medicine, Children’s Hospital of Philadelphia, Philadelphia, PA 1. Address correspondence to Lindy Zhang, MD, Charlotte R. Bloomberg Children’s Center, Johns Hopkins Hospital, 1800 Orleans St, Baltimore, MD 21287. E-mail: lindyzhang{at}jhmi.edu A term boy was born via elective, repeat cesarean delivery to a mother whose prenatal laboratory tests were positive for group B Streptococcus genital infection and negative for human immunodeficiency virus, syphilis, gonorrhea, and chlamydia infections, and showed immunity for rubella. He was the third child born to this mother. The mother had no other diagnosed illnesses, including autoimmune diseases. The cesarean delivery was complicated by extensive adhesions from previous deliveries, but the delivery was atraumatic for the infant. The infant weighed 3.81 kg (82nd percentile for age), and had ABO mismatch with his mother (mother’s blood type was O+, infant’s blood type was A+). By 20 hours of age, the infant developed indirect hyperbilirubinemia (total bilirubin, 7.9 mg/dL). This elevation in bilirubin levels was attributed to ABO isoimmunization. He received 12 hours of phototherapy delivered by a fiberoptic mattress and fluorescent bulbs on an overhead lamp. On postnatal day 2, he had a circumcision, which was complicated by bleeding and required cauterization with silver nitrate. The remainder of his hospital course was uneventful. He was discharged without any ongoing evidence of easy bruising or bleeding and was scheduled for close follow-up with his pediatrician. On postnatal day 6, the infant was presented for his first newborn visit to his pediatrician with jaundice. His total bilirubin level was 19.3 mg/dL. The pediatrician sent the infant to the emergency department for additional evaluation and treatment. There, the infant was found to have severe thrombocytopenia (platelet count, 35 K/mm3) and indirect hyperbilirubinemia (total bilirubin, 20.2 mg/dL; direct bilirubin, 0.3 mg/dL). Mild anemia was present (hemoglobin, 13.8 …