Dubin-Johnson syndrome is best described by which statement?

• A. Impaired excretion of bilirubin into the bile
• B. Hepatic uptake of bilirubin is reduced
• C. Conjugation of bilirubin is defective
• D. Urinary bilirubin is not elevated

Answer: (A)

Dubin-Johnson syndrome centers on a defect in getting conjugated bilirubin out of the liver into the bile. The liver still takes up bilirubin and conjugates it normally, but the canalicular transporter that exports the conjugated form into bile is impaired. Because the conjugated bilirubin can’t be excreted effectively, it builds up in the blood, producing direct (conjugated) hyperbilirubinemia, and some of it is filtered into the urine, leading to elevated urinary bilirubin. This pattern fits best with impaired excretion into the bile, whereas reduced hepatic uptake or defective conjugation would present differently, and the presence of elevated urinary bilirubin argues against a no-elevation scenario.