Gastroenterology and Hepatologyniche
A 26-year-old man is referred for recurrent episodes of yellowing of the eyes, usually after intercurrent illness. He has no pruritus, abdominal pain or weight loss; examination is normal. Total bilirubin is 74 micromol/L (3–20), with 68 micromol/L conjugated, while alkaline phosphatase, alanine aminotransferase and gamma-glutamyl transferase are normal; urine contains bilirubin. Urinary coproporphyrin analysis shows 88% isomer I. Which one of the following is the most likely diagnosis?