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Hemolytic-Uremic Syndrome (HUS)

By

David J. Kuter

, MD, DPhil, Harvard Medical School

Last full review/revision Jul 2020| Content last modified Jul 2020
Click here for the Professional Version

Hemolytic-uremic syndrome (HUS) is a serious disorder that usually occurs in children and involves the formation of small blood clots throughout the body that block the flow of blood to vital organs such as the brain, heart, and kidneys.

  • Symptoms are related to where in the body blood clots form.

  • Diagnosis is based on the person's symptoms and blood tests.

  • Treatment of HUS is support of key body functions and sometimes hemodialysis, and some people may benefit from the drug eculizumab.

HUS is a rare disorder in which many small blood clots (thrombi) form suddenly throughout the body. Hemolytic means that red blood cells break down, and uremic means that kidney injury causes urea (a waste product) to accumulate in the blood. HUS is related to thrombotic thrombocytopenic purpura Thrombotic Thrombocytopenic Purpura (TTP) Thrombotic thrombocytopenic purpura (TTP) is a serious disorder that involves the formation of small blood clots throughout the body that block the flow of blood to vital organs such as the... read more (TTP), but it occurs more often in children and more often causes kidney failure, whereas TTP is more common among adults.

The small blood clots that form in HUS block small blood vessels throughout the body, particularly those in the brain, heart, and kidneys. The blood vessel blockage damages organs and can break apart red blood cells that pass through partially blocked vessels. The blood clots also mean that an abnormally high number of platelets are being used up, which leads to a sharp decrease in the number of platelets in the bloodstream.

Hemolytic-uremic syndrome usually occurs following an intestinal infection that results from ingestion of food contaminated with Escherichia coli O157:H7 or other toxin-producing bacteria.

Symptoms of HUS

In hemolytic-uremic syndrome (HUS), symptoms develop suddenly.

Symptoms in HUS are quite distinct from symptoms of most other forms of thrombocytopenia.

Diagnosis of HUS

  • Blood tests to measure platelet count and clotting

  • Tests to rule out other disorders that cause a low platelet count and bleeding

Doctors suspect hemolytic-uremic syndrome (HUS) when they find a low platelet count in children who have been ill or, less commonly, in those who have taken certain drugs.

Although there are no blood tests that specifically diagnose HUS, doctors do a number of blood tests that, together with people's symptoms, help make the diagnosis. These blood tests often include a complete blood count, tests demonstrating that red blood cells are being destroyed such as examination of a sample of blood under a microscope (blood smear), and tests to determine how well the kidneys are working.

Treatment of HUS

  • Kidney dialysis

  • Sometimes the drug eculizumab

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Anemia is often caused by chronic disease, defined as any disease lasting 3 or more months. Autoimmune disorders, in which the body attacks its own tissues, are a common cause of this type of anemia. Which of the following autoimmune disorders most often causes anemia?
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