Concept
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 type hyperbilirubinemia is a distinct yet similar disorder to Dubin–Johnson syndrome – both diseases cause an increase in conjugated bilirubin. Whereas rotor syndrome differs in that it is a result of impaired hepatocellular storage of conjugated bilirubin that leaks into plasma causing hyperbilirubinemia. Rotor syndrome has many features in common with Dubin–Johnson syndrome, an exception being that the liver cells are not pigmented. The main symptom is a non-itching jaundice. There is a rise in bilirubin in the patient's serum, mainly of the conjugated type. It can be differentiated from Dubin–Johnson syndrome in the following ways: Rotor syndrome may exacerbate toxic side effects of the medication irinotecan. Coproporphyrinogen I 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. Coproporphyrin I, a major coproporphyrin isomer in bile, is transported from the hepatocyte back into the circulation and is excreted in the urine. Thus, urine coproporphyrin is elevated in Rotor syndrome. Cholescintigraphy using sulfobromophthalein (BSP) have shown that the transport capacity of dye into bile is reduced by less than 50%, and the storage capacity in the hepatocytes is decreased more than 5-fold compared with normal values in this disease. Rotor syndrome is inherited in an autosomal recessive manner. The SLCO1B1 and SLCO1B3 genes are involved in Rotor syndrome. 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.
