MCQ: Persistent neonatal jaundice | Diagnosis

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A 5-week-old exclusively breastfed male infant is referred for persistent jaundice. He developed jaundice on the second day of life and required intensive phototherapy during the neonatal period. Despite multiple attempts to discontinue phototherapy, the serum bilirubin repeatedly rises to >25 mg/dL (427 μmol/L) within 24–48 hours. The infant is otherwise thriving with normal growth and development. His stools and urine are normally pigmented, and there is no hepatosplenomegaly.

Investigations reveal:

  • Total bilirubin: 29.2 mg/dL (499 μmol/L)
  • Direct bilirubin: 0.3 mg/dL (5 μmol/L)
  • Hemoglobin: Normal
  • Reticulocyte count: Normal
  • Direct Coombs test: Negative
  • Liver transaminases: Normal

Temporary replacement of breastfeeds with formula for 48 hours results in no significant reduction in serum bilirubin. A subsequent 7-day trial of phenobarbital also fails to lower the bilirubin concentration.

Which of the following is the most likely diagnosis?A. Breast milk jaundice
B. Crigler–Najjar syndrome type I
C. Crigler–Najjar syndrome type II
D. Gilbert syndrome
E. Glucose-6-phosphate dehydrogenase deficiency

Correct answer & Explanation:

Correct Answer

B. Crigler–Najjar syndrome type I

Explanation: Crigler–Najjar syndrome type I

The infant has severe isolated unconjugated hyperbilirubinemia with:

  • Onset in the first few days of life
  • Persistent bilirubin >25 mg/dL
  • No evidence of hemolysis
  • Normal liver function
  • No improvement after temporary interruption of breastfeeding
  • No response to phenobarbital

These findings are classic for Crigler–Najjar syndrome type I, caused by complete absence of UGT1A1 (UDP-glucuronosyltransferase) activity.

Patients require prolonged phototherapy during infancy, but liver transplantation is the only definitive treatment because they are at high risk of bilirubin encephalopathy (kernicterus).

Why the other options are incorrect

A. Breast milk jaundice

  • Usually appears after the first week of life and rarely requires prolonged intensive phototherapy.
  • Bilirubin generally falls after 24–48 hours of temporary formula feeding.
  • Phenobarbital responsiveness is not a defining feature.

C. Crigler–Najjar syndrome type II

  • Caused by partial UGT1A1 deficiency.
  • Bilirubin levels are generally lower than in type I.
  • Responds to phenobarbital, with a significant fall in bilirubin.

D. Gilbert syndrome

  • Causes mild intermittent unconjugated hyperbilirubinemia, usually presenting later in childhood or adolescence.

E. Glucose-6-phosphate dehydrogenase deficiency

  • Produces unconjugated jaundice due to hemolysis.
  • Reticulocytosis and other evidence of hemolysis are typically present.

FCPS / MRCPCH High-Yield Pearl

The combination of:

  • Severe unconjugated hyperbilirubinemia (>25 mg/dL)
  • Normal liver function
  • No hemolysis
  • No reduction after temporary formula feeding
  • No response to phenobarbital

strongly indicates Crigler–Najjar syndrome type I, distinguishing it from breast milk jaundice and Crigler–Najjar syndrome type II.

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