An otherwise healthy 3-week-old boy is brought to the physician’s office because of jaundice and dark urine for the past 2 weeks. He has hepatomegaly, and his stools are loose, clay-colored, and acholic. Serum conjugated bilirubin concentration is increased. Which of the following is the most likely cause of the hyperbilirubinemia?
a.Defect in cholesterol synthesis
b.Deficiency of glucuronosyltransferase
c.Hemolysis
d.Inflammation of the terminal ileum
e.Obstruction of the biliary system
Correct answer
Obstruction of the biliary system
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correct answer: E
The key point here is the increase in conjugated bilirubin, demonstrating that the liver is functioning properly. Combined with hepatomegaly, jaundice, bilirubinuria, and the described abnormal stools, this conjugated hyperbilirubinemia suggests an obstruction of the biliary system (E).
A defect in cholesterol synthesis (A) could adversely affect bile acid production and result in acholic, loose, clay-colored stools. However, such a defect should not affect bilirubin excretion and thus would not explain the hyperbilirubinemia seen in this infant. Furthermore, these defects in cholesterol synthesis are much less common than obstructions of the biliary system (E).
A deficiency of glucuronosyltransferase (B) is suggestive of Gilbert’s syndrome (GS) or the much less common Crigler-Najar syndrome (CDS). However, in GS and CDS the hyperbilirubinemia is due to unconjugated, not conjugated, bilirubin. Unconjugated bilirubin is insoluble, and therefore would not appear in the urine.
Hemolysis ©, like the glucuronosyltransferase disorders, results in an unconjugated, not conjugated, hyperbilirubinemia. Again, unconjugated bilirubin would not be seen in the urine.
Inflammation of the terminal ileum (D) in an infant with loose, clay-colored stools suggests celiac disease. Though iron absorption (and many other substances) may be affected, celiac disease should not cause hyperbilirubinemia. Crohn’s disease would also affect the terminal ileum and may have symptoms of malabsorption, but it too should not cause hyperbilirubinemia. Further, onset of Crohn’s is usually not seen until 15 – 30 years of age.