USMLE PRACTICE QUESTION OF THE WEEK
Question for August 15, 2025
A 6-month-old infant is brought to the clinic for evaluation of persistent jaundice. He was born at term and has been breastfed exclusively. Physical examination shows hepatomegaly and scleral icterus. Laboratory studies reveal elevated conjugated bilirubin and normal gamma-glutamyltransferase (GGT) levels.
Which of the following is the most likely diagnosis?
Which of the following is the most likely diagnosis?
Correct Answer:
D. Dubin-Johnson syndrome
Correct Answer Explanation:
This infant has conjugated hyperbilirubinemia with a normal GGT, which suggests Dubin-Johnson syndrome, a benign condition characterized by defective hepatic excretion of conjugated bilirubin.
Why These Are Incorrect:
- A. Alpha-1 antitrypsin deficiency causes neonatal hepatitis but often shows elevated transaminases and progressive liver disease.
- B. Biliary atresia shows elevated conjugated bilirubin but also has elevated GGT and worsening cholestasis.
- C. Breast milk jaundice causes unconjugated hyperbilirubinemia.
- E. Gilbert syndrome causes mild unconjugated hyperbilirubinemia triggered by stress.