aHUS (atypical hemolytic uremic syndrome)

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aHUS (atypical hemolytic uremic syndrome) is a very rare genetic disease that causes tiny blood clots to form in your blood vessels, blocking blood flow to important organs. aHUS can cause kidney failure, heart disease and other serious health problems. While there is no known cure for aHUS, it can be treated.
Medically reviewed by
AKF's Medical Advisory Committee
Last updated
June 26, 2024

What is aHUS?

aHUS (atypical hemolytic uremic syndrome) is a very rare disease that causes tiny blood clots to form in the small blood vessels of your body. These blood clots can block blood flow to important organs, such as your kidneys. This can damage your kidneys and lead to kidney failure.

aHUSis a form of thrombotic microangiopathy (TMA), a group of conditions that happens when these tiny blood clots form. Research into the different causes of TMA is still ongoing, and the names and words you hear when talking about aHUS and TMA might change. Some terms you might hear your provider use when referring to aHUS include:  

  • Complement-Mediated TMA  
  • Complement disease 
  • Primary TMA 

As research continues and the understanding of TMA moves forward, the language you hear from your provider may change. This can be confusing and frustrating, but you can always ask your doctor to clarify or review anything you're confused about.  

What are the signs and symptoms of aHUS?

In the beginning, aHUS may feel like a common virus — you may feel sick and low on energy. You may also have:

  • Diarrhea
  • Nausea or throwing up
  • Pain in your belly
  • Confusion

What health conditions are signs that I may have aHUS?

The three most common signs of aHUS are:

  • Kidney damage or kidney failure
  • Hemolytic anemia: A kind of anemia (not enough red blood cells in your body)
  • Thrombocytopenia: Not enough blood platelets in your body. Platelets are colorless blood cells that help your blood clot (stick together) to stop bleeding.

Most people with aHUS will have all three of these signs. 

What can happen when aHUS gets worse?

As aHUS gets worse, the tiny blood clots that form in your small blood vessels can slow down or cut off blood flow to your organs. This can cause:

  • Kidney failure
  • Swelling of your legs, ankles and feet
  • Blood in your urine (hematuria)
  • Very high blood pressure
  • Heart disease or heart attack
  • Stroke

What causes aHUS?

aHUS is caused by a change (mutation) in the genes that help control your immune system. However, having a gene mutation alone usually will not cause the disease. In most cases, it takes a "triggering event" for aHUS to cause symptoms in your body. Some examples of aHUS triggers are:

blue dna illustration with photo
  • Pregnancy
  • Infections from viruses or bacteria
  • Cancer
  • Certain medicines

Not all people that are diagnosed with aHUS have a gene mutation that shows up on a test. Researchers think this is because not all gene mutations linked to aHUS have been discovered yet. 

Who can get aHUS?

aHUS is very rare, which means very few people are diagnosed with it. The aHUS Foundation estimates that fewer than 625 people in the United States have aHUS.  You are more likely to get aHUS if you have a family history, such as a parent, grandparent or sibling with the disease.


Rare disease spotlight: Diagnosis, treatment and management of aHUS


Rare disease spotlight: Diagnosis, treatment and management of aHUS

aHUS (atypical hemolytic uremic syndrome) is a rare disease that causes too many blood clots to form in your blood vessels. Watch our webinar and learn more about aHUS, how it is diagnosed, and treatment options.

How do doctors treat aHUS?

Doctors may treat aHUS with:

  • Medicines that can raise the number of red blood cells and platelets in your body 
  • Medicines to protect your kidneys
  • Plasma therapy, which means exchanging a portion of your blood with fresh, healthy blood. Plasma therapy works for treating aHUS in some people but does not work for everyone.

aHUS affects everyone differently. Work with a nephrologist (kidney doctor) and a hematologist (blood doctor) to make a treatment plan that is right for you.

How can I prevent aHUS?

Because aHUS is a genetic disease, there is no known way to prevent it. However, treatment can help you manage aHUS. The best way to prevent aHUS from damaging your organs and harming your health is to follow the treatment plan you and your doctors make together.

How long can I live with aHUS?

aHUS is a lifelong condition and there currently is no cure. How long you may live (your life expectancy) depends on many things, such as:

  • Your age when diagnosed with aHUS
  • How well you follow your treatment plan
  • Your overall health

This education content is made possible by Alexion Pharmaceuticals, Inc.