BackgroundABO blood group incompatibility, neonatal sepsis, G-6-PD deficiency, thyroid dysfunction, and hereditary spherocytosis are all probable causes of neonatal hyperbilirubinemia. However, the etiology of some hyperbilirubinemia is extremely complicated, which may be caused by multiple factors, resulting in severe jaundice. We report a case of severe jaundice due to three causes, showing the significance for the investigation of the etiology of neonatal hyperbilirubinemia.Case presentationAt 96 h of life, a full-term and vaginal delivery male infant with yellowish discoloration of body was transferred to our hospital. When he entered neonatal intensive care unit on the fourth day after birth, he developed jaundice and the transcutaneous bilirubin was 28 mg/dl. Total bilirubin was 540.2 μmol/L, while the indirect bilirubin was 516.7 μmol/L. Both parents and the baby’s blood types were O Rh(D +), and direct coomb’s test was negative. But mother’s indirect coomb’s test was positive. Investigating for minor blood group revealed that the father’s blood type of Rh was CCDee, the mather’s was ccDEE, and CcDEe for the baby. After intensive phototherapy and double volume exchange transfusion, the total bilirubin remained at 303 μmol/L. At day 10, the bilirubin level was 303.5 μmol/L, intensive phototherapy was continued, and intravenous immunoglobulin was used again. The test for thyroid hormones at day 10, the TSH was 13.334mIU/L. And the screening for congenital hypothyroidism showed the TSH was 33mIU/L. Because of the palpable abdominal mass, ultrasound and MRI was done, showed a huge mass in the right adrenal gland. Brainstem auditory evoked potential was performed at day 7, which indicated hearing impairment (65db for left ear and 70db for the right). Euthyrox and intermittent phototherapy were given as following treatment. The jaundice did not subside until the 12th day.ConclusionEven if their parents' ABO blood group and Rh (d) are consistent, a Coomb test is required for newborns with hyperbilirubinemia since they may have minor blood group incompatibilities. When bilirubin rises rapidly or the clinical treatment effect is inadequate, additional causes should be aggressively screened. Adrenal ultrasound should be performed on newborns with palpable abdominal mass, anemia and jaundice to determine whether there is adrenal hemorrhage.