biology

Rotor syndrome

Rotor syndrome is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Rotor syndrome rather than just read about it. In short: 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 d…

Key takeaways

Rotor syndrome belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Rotor syndrome to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Rotor syndrome from memory before moving on to harder problems.

Reference excerpt

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, but Rotor syndrome differs in that it is a result of impaired hepatocellular storage of conjugated bilirubin that leaks into plasma causing hyperbilirubinemia.

Signs and symptoms 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.

Pathophysiology

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.

Genetics

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. 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.

Diagnosis 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. Serological abnormalities in Rotor syndrome only include elevated total serum bilirubin (typically elevated between 2 and 5 mg/dL but may be as high as 20 mg/dL). Most of the time, alanine aminotransferase, aspartate aminotransferase, gamma-glutamyl transferase, and alkaline phosphatase levels are normal, but mild elevations can be seen. If any of these lab values are markedly elevated, investigation for other, more serious conditions is warranted. Imaging studies cannot diagnose Rotor syndrome but can help rule out other diseases that cause hyperbilirubinemia. For example, ultrasound of the liver and the biliary tree can help investigate the causes of extra-hepatic biliary obstruction. The gallbladder is visualized on oral cholecystography in Rotor syndrome while it is not visualized in Dubin Johnson syndrome. Ultimately, the best method of diagnosing the disease is the analysis of urine coproporphyrin excretion. The total urine coproporphyrin excretion in Rotor syndrome has a 2- to 5-fold elevation, with 65% constituting coproporphyrin I.

Treatment Rotor syndrome is a benign disease requiring no treatment. Jaundice is a lifelong finding, but the disease is not associated with morbidity or mortality, and life expectancy is not affected. Most individuals with Rotor syndrome are born to consanguineous couples and its diagnosis may coincidently identify consanguinity. Distinguishing Rotor syndrome from other more serious disorders is important to avoid unnecessary workup and interventions. It is also critical to reassure and calm patients or family members of patients with Rotors syndrome that the condition is benign.

History Rotor syndrome is named after the Filipino internist Arturo Belleza Rotor (1907–1988).

See also Jaundice Bilirubin metabolism Gilbert's syndrome Crigler–Najjar syndrome

References

External links Hyperbilirubinemia, Conjugated at eMedicine Rotor syndrome at NIH's Office of Rare Diseases Mentioned in MedlinePlus Encyclopedia: Jaundice – yellow skin

Illustrations

Worked examples

Example 1 — a first encounter with Rotor syndrome

Start with the simplest possible case. Write down what Rotor syndrome claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Rotor syndrome before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Rotor syndrome ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Rotor syndrome

In research: Rotor syndrome appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Rotor syndrome in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Rotor syndrome is common in secondary-school and first-year university syllabi. It links to neighbouring topics Autosomal recessive disorders, Heme metabolism disorders, Hepatology, so understanding it makes those chapters shorter.
In everyday life: Look for Rotor syndrome outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Rotor syndrome in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Rotor syndrome means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Rotor syndrome out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Rotor syndrome in simple terms?

Why does Rotor syndrome matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Rotor syndrome?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Rotor syndrome.