A 30-year-old man has persistent conjugated hyperbilirubinemia of 3 mg/dL with otherwise normal liver function tests including a normal alkaline phosphatase. Liver biopsy shows coarse dark-brown granular pigment within hepatocytes. Urinary coproporphyrin total excretion is normal but the proportion of coproporphyrin I is markedly increased. The MOST likely diagnosis is:

• A Rotor syndrome
• B Primary biliary cholangitis
• C Progressive familial intrahepatic cholestasis type 1
• D Dubin-Johnson syndrome ✓

Explanation

Dubin-Johnson syndrome results from a canalicular MRP2 transport defect causing impaired biliary excretion of conjugated bilirubin. It features benign conjugated hyperbilirubinemia, a normal alkaline phosphatase, black pigmented liver on biopsy, and a characteristic shift of urinary coproporphyrin toward coproporphyrin I with normal total excretion. Rotor syndrome lacks hepatic pigment and shows increased total urinary coproporphyrin, which kills that distractor.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.