A healthy 24-year-old man undergoing routine testing has a conjugated hyperbilirubinaemia of 3 mg/dL. Liver biopsy shows coarse dark brown pigment granules within hepatocytes, predominantly in centrilobular zones. He has no pruritus, no haemolysis, and a normal life expectancy. Defective transport across which protein explains this disorder?

• A Canalicular multidrug resistance-associated protein 2 (MRP2) ✓
• B UDP-glucuronosyltransferase 1A1
• C Organic anion transporting polypeptide (OATP) on the sinusoidal membrane
• D ATP8B1 flippase

Explanation

Dubin-Johnson syndrome results from mutation of ABCC2 encoding MRP2, the canalicular transporter for conjugated bilirubin, producing benign conjugated hyperbilirubinaemia with black epinephrine-derived pigment in hepatocytes. UDP-glucuronosyltransferase defects cause the unconjugated hyperbilirubinaemias of Gilbert and Crigler-Najjar syndromes. OATP defects underlie Rotor syndrome, which lacks pigment, and ATP8A1 mutations cause familial intrahepatic cholestasis with pruritus.

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.