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Hemolytic-Uremic Syndrome (HUS)

By

David J. Kuter

, MD, DPhil, Harvard Medical School

Last full review/revision Jun 2022| Content last modified Sep 2022
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 (thrombocytopenia).

Hemolytic-uremic syndrome usually occurs following an intestinal infection that results from ingestion of food contaminated with the bacteria Escherichia coli O157:H7 E. coli O157:H7 infection Escherichia coli (E. coli) are a group of gram-negative bacteria that normally reside in the intestine of healthy people, but some strains can cause infection in the digestive... read more 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

  • Blood and urine tests to measure kidney function

  • 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

  • Usually kidney dialysis

  • Sometimes the drugs eculizumab or ravulizumab

About half of children with hemolytic-uremic syndrome temporarily require kidney dialysis Dialysis Dialysis is an artificial process for removing waste products and excess fluids from the body, a process that is needed when the kidneys are not functioning properly. There are a number of reasons... read more Dialysis , in which a dialysis machine removes waste products from the blood. Most often, the kidneys recover, but some children have permanent kidney damage. Eculizumab and ravulizumab are drugs that suppress complement Complement System One of the body's lines of defense (immune system) involves white blood cells (leukocytes) that travel through the bloodstream and into tissues, searching for and attacking microorganisms and... read more , a component of the immune system. They reduce the rate of kidney damage, and in some people, they may rapidly restore kidney function. People who take eculizumab or ravulizumab are at higher risk than normal for meningococcal meningitis Meningococcal Infections Meningococcal infections are caused by the bacteria Neisseria meningitidis (meningococci) and include meningitis and sepsis. Infection is spread by direct contact with nasal and throat... read more Meningococcal Infections , so they should receive the meningococcal vaccine Prevention Meningococcal infections are caused by the bacteria Neisseria meningitidis (meningococci) and include meningitis and sepsis. Infection is spread by direct contact with nasal and throat... read more Prevention to prevent meningococcal infections.

Drugs Mentioned In This Article

Generic Name Select Brand Names
SOLIRIS
ULTOMIRIS
NOTE: This is the Consumer Version. DOCTORS: CLICK HERE FOR THE PROFESSIONAL VERSION
CLICK HERE FOR THE PROFESSIONAL VERSION
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