- Dubin-Johnson Syndrome is the result of a hereditary mutation in the protein which actively transports conjugated bilirubin across the hepatocyte membrane and into the bile canaliculi. Because the actual enzymatic process of bilirubin conjugation is not affected (See: Heme Degradation) bilirubin is conjugated normally in hepatocytes but cannot be properly excreted due to the transport defect. Consequently, a conjugated hyperbilirubinemia ensues resulting signs of jaundice. Additionally, the liver of patients with Dubin-Johnson syndrome is characteristically very dark owing to the deposition of epinephrine metabolites which are also not excreted normally. Other than the signs of jaundice there are no other significant clinical consequences to this disorder.