A 2-day-old Asian girl is evaluated in the newborn nursery due to jaundice. She was born at 40 weeks gestation to a 30-year-old mother via uncomplicated vaginal delivery. Membranes ruptured spontaneously an hour prior to delivery. Prenatal laboratory testing was normal. Group B streptococcus screen was negative. Maternal blood group is AB, Rh D-positive. The patient has been exclusively breastfeeding with good latch, voiding appropriately, and passing meconium. She has 2 healthy older siblings, both of whom required phototherapy in the first few days of life. Weight and length are at the 50th percentile. Vital signs are normal. On examination, jaundice of the face and neck is present. The remainder of the examination is unremarkable. Laboratory results at 34 hours of life are as follows: Which of the following mechanisms is contributing to this newborn's condition?

Question

A 2-day-old Asian girl is evaluated in the newborn nursery due to jaundice.  She was born at 40 weeks gestation to a 30-year-old mother via uncomplicated vaginal delivery.  Membranes ruptured spontaneously an hour prior to delivery.  Prenatal laboratory testing was normal.  Group B streptococcus screen was negative.  Maternal blood group is AB, Rh D-positive.  The patient has been exclusively breastfeeding with good latch, voiding appropriately, and passing meconium.  She has 2 healthy older siblings, both of whom required phototherapy in the first few days of life.  Weight and length are at the 50th percentile.  Vital signs are normal.  On examination, jaundice of the face and neck is present.  The remainder of the examination is unremarkable.  Laboratory results at 34 hours of life are as follows:  Which of the following mechanisms is contributing to this newborn's condition?

Quizplus · Accepted Answer

11ec25c8_d686_fb82_bc81_e720d134fdad_MD0003_00 Almost all newborns on days 2-4 of life have physiologic jaundice due to indirect hyperbilirubinemia. The following physiologic differences in bilirubin metabolism account for this finding: At birth, fetal red blood cells (RBCs) are increased (hematocrit 50%-60%) with a shortened life span (90 days), resulting in high RBC turnover and increased bilirubin production.Hepatic bilirubin clearance is decreased because uridine diphosphogluconurate glucuronosyltransferase (UGT) activity does not reach adult levels until age 2 weeks. This hepatic enzyme conjugates bilirubin, making it soluble (ie, excretable). Eastern Asian newborns have decreased UGT compared to that of other ethnicities.Enterohepatic recycling is increased because the low bacterial load in the newborn gut results in slower conversion of bilirubin to urobilinogen for fecal excretion. At birth, fetal red blood cells (RBCs) are increased (hematocrit 50%-60%) with a shortened life span (90 days), resulting in high RBC turnover and increased bilirubin production. Hepatic bilirubin clearance is decreased because uridine diphosphogluconurate glucuronosyltransferase (UGT) activity does not reach adult levels until age 2 weeks. This hepatic enzyme conjugates bilirubin, making it soluble (ie, excretable). Eastern Asian newborns have decreased UGT compared to that of other ethnicities. Enterohepatic recycling is increased because the low bacterial load in the newborn gut results in slower conversion of bilirubin to urobilinogen for fecal excretion. Physiologic jaundice of the newborn is benign and resolves by age 1-2 weeks. Frequent feeding promotes gut colonization and fecal excretion. Phototherapy may be indicated for rapidly rising levels of bilirubin to prevent kernicterus. (Choice A) Beta thalassemia (decreased beta globin chain production) can cause hemolysis and unconjugated hyperbilirubinemia. However, newborns are asymptomatic because they have mostly fetal hemoglobin (α₂, γ₂). After age 6 months, symptoms of hemolytic anemia emerge as adult hemoglobin (α₂, β₂) is produced. (Choice B) Glucose-6-phosphate dehydrogenase deficiency can present with hemolysis and hyperbilirubinemia. This infant has a normal hematocrit level and no evidence of hemolysis on peripheral smear (eg, bite cells). (Choice D) Biliary atresia is characterized by extrahepatic bile duct fibrosis and obliteration. Patients have normal hepatic conjugation but impaired bilirubin excretion, leading to direct hyperbilirubinemia (unlike this patient). In addition, symptoms (eg, jaundice, acholic stools) develop at age 2-8 weeks. (Choice E) Hereditary spherocytosis is an RBC membrane defect in which RBCs lose their biconcave shape and are prone to hemolysis. Indirect hyperbilirubinemia and anemia are seen due to elevated RBC turnover. This patient has normal RBC morphology on peripheral smear. (Choice F) Isoimmune-mediated hemolysis is the destruction of neonatal RBCs by maternal antibodies. Mothers who are Rh D-negative or whose ABO blood group is different from their infant may have antibodies that cause neonatal hemolysis and indirect hyperbilirubinemia. Mothers who have blood group AB, Rh D-positive do not produce such antibodies. antibodies Educational objective: Physiologic jaundice of the newborn is a common, benign cause of indirect hyperbilirubinemia on days 2-4 of life. Mechanisms include increased bilirubin production, decreased bilirubin clearance, and increased enterohepatic recycling. References: Neonatal hyperbilirubinemia in the low-intermediate-risk category on the bilirubin nomogram. (http://www.ncbi.nlm.nih.gov/pubmed/22926183) Hyperbilirubinemia in the newborn. (http://www.ncbi.nlm.nih.gov/pubmed/21807875)

A 2-Day-Old Asian Girl Is Evaluated in the Newborn Nursery