What may be the cause of neonatal physiological jaundice of the hepatic type?

What may be the cause of neonatal physiological jaundice of the hepatic type?

• A. Hemolytic episode caused by an ABO incompatibility
• B. Stricture of the common bile duct
• C. Hemolytic episode caused by an Rh incompatibility
• D. Deficiency in the bilirubin conjugation enzyme system

Answer: (D)

Neonatal physiological jaundice of the hepatic type comes from the newborn’s liver not yet having full ability to conjugate bilirubin. The key enzyme, UDP-glucuronosyltransferase, is immature in newborns, especially in preterm infants, so bilirubin remains largely in its unconjugated form (indirect bilirubin) and builds up in the blood until the enzyme system matures. This hepatic-conjugation defect is what characterizes the hepatic-type jaundice seen in newborns. This fits with the cause described as a deficiency in the bilirubin conjugation enzyme system, since the problem is the liver’s limited capacity to conjugate bilirubin rather than excessive bilirubin production from red blood cell breakdown or a biliary blockage. Hemolytic conditions due to ABO or Rh incompatibilities increase bilirubin by increasing production (prehepatic), not by a lack of conjugation, and a common bile duct stricture would produce conjugated (direct) hyperbilirubinemia due to obstruction, not the typical neonatal hepatic-type picture.

Neonatal physiological jaundice of the hepatic type comes from the newborn’s liver not yet having full ability to conjugate bilirubin. The key enzyme, UDP-glucuronosyltransferase, is immature in newborns, especially in preterm infants, so bilirubin remains largely in its unconjugated form (indirect bilirubin) and builds up in the blood until the enzyme system matures. This hepatic-conjugation defect is what characterizes the hepatic-type jaundice seen in newborns.

This fits with the cause described as a deficiency in the bilirubin conjugation enzyme system, since the problem is the liver’s limited capacity to conjugate bilirubin rather than excessive bilirubin production from red blood cell breakdown or a biliary blockage. Hemolytic conditions due to ABO or Rh incompatibilities increase bilirubin by increasing production (prehepatic), not by a lack of conjugation, and a common bile duct stricture would produce conjugated (direct) hyperbilirubinemia due to obstruction, not the typical neonatal hepatic-type picture.