Rotor syndrome

Rotor syndrome results from mutations in the OATP1B1 and OATP1B3 transporters (encoded by SLCO1B1 and SLCO1B3 genes), which are responsible for hepatocellular uptake of bilirubin and other organic anions from the sinusoidal blood. Loss of both transporters leads to impaired storage of conjugated bilirubin within hepatocytes, causing it to reflux back into the bloodstream, resulting in mixed direct and indirect hyperbilirubinemia. Unlike Dubin-Johnson syndrome (caused by MRP2/ABCC2 mutation affecting bilirubin excretion into bile), Rotor syndrome liver histology is normal—there is no black pigment deposition, distinguishing it grossly and histologically. Patients present with chronic, mild jaundice, usually detected incidentally or during times of stress (illness, pregnancy), but are otherwise asymptomatic with normal liver function tests aside from bilirubin. Urinary coproporphyrin levels are elevated (total urinary coproporphyrin excretion increased, with increased proportion of coproporphyrin I), which helps distinguish it from Dubin-Johnson syndrome (which shows normal total urinary coproporphyrin but elevated coproporphyrin I fraction). No treatment is necessary; prognosis is excellent with normal life expectancy. It's a classic exam distractor paired with Dubin-Johnson syndrome to test students' ability to differentiate hereditary hyperbilirubinemias based on gross/histologic liver appearance and urinary coproporphyrin patterns.