A male neonate was born at 38+5 weeks gestation to a 40-year-old gravida 2, para 2, blood group O Rh positive mother, via spontaneous vaginal delivery. The pregnancy was uncomplicated. Both his mother and father were non-consanguineous Japanese parents without any past medical history. His sibling (2-year-old girl) did not have any jaundice. His birth weight was 3460 g (appropriate for gestational age), and his Apgar score were 9 at 1 min and 9 at 5 min. He was exclusively breastfed, although the mother's breast milk secretion was not sufficient.
On day 2, he looked icteric, and a blood test was performed. His serum total bilirubin (STB) was 20.1 mg/dl (the indication of phototherapy according to the criteria of Kobe University, Japan: 12 mg/dl) (Department of Pediatrics, Kobe University Graduate School of Medicine), his serum direct bilirubin was 1.29 mg/dl (normal upper limit: 0.6 mg/dl). He was transferred to our NICU due to severe jaundice and was admitted on the same day.
Physical examinations revealed a body weight of 3217 g (7.0% weight loss). His vital signs were within normal limits. His bulbar conjunctiva and skin were icteric, and no hepatosplenomegaly was found. His blood type was group B, Rh positive. A complete blood count (CBC) revealed hemoglobin (Hb) of 12.6 g/dl and, a reticulocyte count of 10.9%; a blood smear for red cell morphology was within normal limits, without spherocytosis or red cell fragments. Chemistry showed no abnormal findings, except for STB (18.7 mg/dl). Direct and indirect Coombs' tests were negative. Blood culture was negative. Urinalysis did not show any occult blood, urobilinogen or bacteria. Chest and abdominal radiographs were normal. Head ultrasonography (US) showed no intracranial hemorrhage and abdominal US did not reveal any adrenal hemorrhage.
An exchange transfusion was reserved because of the patient's STB (the criteria for indication was an STB>20 mg/dl, according to Kobe University), and phototherapy was initiated. Table 1 shows the course of the blood test results and management. A total of 15 ml/kg of red blood cells (RBCs) was transfused on 2 consecutive days (days 16 and days 17). After the RBCs transfusion, a CBC showed 14.3 g/dl of Hb. On day 16, an erythrocyte osmotic fragility test, CD55 and CD59 were within normal limits. He was referred to Tokyo Women's Medical University to further investigate any erythrocyte disorders. His glucose-6-phosphate dehydrogenase activity was 3.06 IU/gHb (his father and mother's activity was not available), while the normal level is 11.0 IU/gHb. The patient was diagnosed as having a G6PD deficiency. Two weeks after birth, his jaundice and anemia became stable without any treatment and he was discharged on day 21 with an STB value of 14.7 mg/dl, Hb of 12.9 g/dl and a reticulocyte count of 2.0%.