What is a key laboratory finding in Dubin-Johnson syndrome?

Dubin-Johnson syndrome is characterized by a genetic defect that leads to an impaired secretion of conjugated bilirubin from hepatocytes into the bile. As a result, individuals with this syndrome present with conjugated hyperbilirubinemia, which is the hallmark laboratory finding. The elevated levels of conjugated bilirubin occur due to the accumulation of this substance in the bloodstream since it cannot be effectively cleared by the liver.

In Dubin-Johnson syndrome, alkaline phosphatase levels typically remain normal or may be mildly elevated, so elevated alkaline phosphatase is not a key finding. Increased cholesterol levels are also not a classic feature of this condition. Additionally, while liver function might be mildly affected, serum albumin levels usually remain normal, highlighting that low serum albumin is not a characteristic finding either. Thus, the identifying laboratory test for Dubin-Johnson syndrome is indeed the presence of conjugated hyperbilirubinemia.