Dubin Johnson Syndrome (DJS) is a rare autosomal recessive genetic disorder, which is characterized by an increase of conjugated bilirubin without elevation of liver enzymes. This conjugated hyperbilirubinemia is the result of defects in the transfer of anionic conjugates from hepatocytes into the bile. Bilirubin is conjugated, but not secreted into the bile, leading to a cellular accumulation and eventful reflux of the conjugated bilirubin into the circulation.

Patients with DJS are mostly asymptomatic. The major symptom of the condition is mild jaundice, which although may appear only at puberty or adulthood and may remain throughout life. The jaundice may be aggravated by pregnancy, alcohol, or oral contraceptives. In addition, the accumulation of melanin-like pigment in the liver in DJS tends to provide a dark brown appearance to the organ. Another hallmark of the condition is an increase in the corpoporphyrin I:corpoporphyrin III ratio. In addition, a majority of the patients have been found to have reduced prothrombin activity, due to lower levels of Factor VII.

Diagnosis of the condition makes use of measurements of serum bilirubin and urinary corpoporphyrin levels. Liver biopsy may also be required. Since DJS is a benign condition, treatment is usually not required. Life expectancy is normal.

DJS results from mutations in the human Canalicular Multispecific Organic Anion Transporter (cMOAT), an ATP binding cassette superfamily member, which plays a role in mediating active hepetobiliary excretion of numerous organic anions. Mutations in the gene have been found to result in impaired transport of the non-bile salt anions across the canalicular membrane of the hepatocytes, resulting in the conjugated hyperbilirubinemia and accumulation of the hepatocellular pigment, characteristic of DJS. Mutations in the functionally critical ATP binding region of the protein are especially important.