Rotor syndrome
Rotor syndrome is a rare inherited liver disorder that causes lifelong elevation of conjugated bilirubin, usually without symptoms or liver damage.
Conjugated hyperbilirubinemia: Elevated blood levels of bilirubin that has been conjugated with glucuronic acid in the liver. Rotor syndrome produces this laboratory pattern despite usually causing no illness.
Bilirubin metabolism: The breakdown, transport, chemical processing, and excretion of bilirubin in the body. Rotor syndrome alters the liver’s handling of bilirubin after conjugation.
Gilbert syndrome: A common inherited condition causing mild, intermittent unconjugated hyperbilirubinemia due to reduced bilirubin conjugation. It is usually benign like Rotor syndrome, but raises unconjugated rather than conjugated bilirubin.
Urinary coproporphyrin: Coproporphyrin pigments measured in urine as indicators of heme metabolism and hepatic transport. Rotor syndrome increases total urinary coproporphyrin, a clue to its diagnosis.
Bilirubin: A yellow pigment formed during the breakdown of heme, processed by the liver and excreted in bile. Its conjugated form accumulates in blood in Rotor syndrome.
Bilirubin conjugation: The liver’s attachment of glucuronic acid to bilirubin, making it more water-soluble for excretion. Conjugation remains intact, distinguishing Rotor syndrome from defects in bilirubin processing.
Crigler–Najjar syndrome: A rare inherited disorder of bilirubin conjugation that causes severe unconjugated hyperbilirubinemia. It affects conjugation itself, unlike Rotor syndrome’s transport defect.
Coproporphyrin I: A coproporphyrin isomer whose proportion in urine rises in several inherited bilirubin transport disorders. Its urinary proportion helps distinguish Rotor syndrome from other causes of conjugated hyperbilirubinemia.
Hepatic organic anion transporters: Membrane proteins that move bilirubin and other organic anions into and out of liver cells. Defective reuptake transport contributes to Rotor syndrome’s impaired hepatic handling of conjugated bilirubin.
Hepatocyte: The main functional cell of the liver, responsible for metabolism, transport, and secretion. Rotor syndrome reflects altered transport functions in these liver cells.