Rotor syndrome

Rotor syndrome (also known as Rotor type hyperbilirubinemia) is a rare cause of mixed direct (conjugated) and indirect (unconjugated) hyperbilirubinemia, relatively benign, autosomal recessive bilirubin disorder characterized by non hemolytic jaundice due to the chronic elevation of predominantly conjugated bilirubin. Rotor syndrome Dubin–Johnson syndrome
appearance of liver normal histology and appearance liver has black pigmentation
gallbladder visualization gallbladder can be visualized by oral cholecystogram gallbladder cannot be visualized
total urine coproporphyrin content high with <70% being isomer 1 normal with >80% being isomer 1 (normal urine contains more of isomer 3 than isomer 1)

Rotor syndrome may exacerbate toxic side effects of the medication irinotecan.

Rotor syndrome is caused by mutations in two proteins responsible for transporting bilirubin and other compounds from the blood to the liver to be metabolized and cleared from the body. Mutations in both genes are required for the condition to occur. The SLCO1B1 and SLCO1B3 genes provide instructions for making similar proteins, called organic anion transporting polypeptide 1B1 (OATP1B1) and organic anion transporting polypeptide 1B3 (OATP1B3), respectively. Both proteins are found in liver cells; they transport bilirubin and other compounds from the blood into the liver so that they can be cleared from the body. In the liver, bilirubin is dissolved in a digestive fluid called bile and then excreted from the body. The SLCO1B1 and SLCO1B3 gene mutations that cause Rotor syndrome lead to abnormally short, nonfunctional OATP1B1 and OATP1B3 proteins or an absence of these proteins. Without the function of either transport protein, bilirubin is less efficiently taken up by the liver and removed from the body. The buildup of this substance leads to jaundice in people with Rotor syndrome.

Increased conjugated hyperbilirubinemia is the hallmark for diagnosing Rotor syndrome. There is no distinct black pigmentation of the liver as seen in a similar, Dubin Johnson Syndrome. Genes, SLCO1B1 and SLCO1B3 that result in complete functional deficiencies of both protein products (OATP1B1 and OATP1B3, respectively), are also present. Rotor syndrome is largely a diagnosis of exclusion.