TABLE 45.1 CAUSES OF UNCONJUGATED HYPERBILIRUBINEMIA Excess bilirubin production Intravascular hemolysis Intrinsic Glucose-6-phosphate dehydrogenase deficiency, pyruvate kinase deficiency Sickle cell disease, thalassemia Hereditary spherocytosis, hereditary elliptocytosis Extrinsic Isoimmunization (ABO incompatibility, Rh disease) Infection Hemolytic anemia (autoimmune, microangiopathic, drug induced) Extravascular hemolysis Cephalohematoma Swallowed blood during birth Concealed hematoma (intracranial, pulmonary, intra-abdominal) Polycythemia Hypersplenism Decreased bilirubin conjugation Physiologic jaundice Gilbert syndrome, Crigler–Najjar syndrome, Lucey–Driscoll syndrome Galactosemia Endocrine disorders (congenital hypothyroidism, infant of a diabetic mother) Breast milk jaundice Impaired bilirubin excretion Breast-feeding jaundice Bowel obstruction Infection (sepsis, TORCH) Toxin mediated Decreased Bilirubin Conjugation Incomplete maturation of conjugation enzymes in the newborn infant’s liver is the most common etiology of mild hyperbilirubinemia, with approximately 60% of neonates manifesting clinical signs of physiologic jaundice Physiologic jaundice