What is aHUS? 10 facts about a very rare but serious kidney disease

The two most common causes of kidney disease are diabetes and high blood pressure. However, there are many other causes of kidney disease and kidney failure, and the rarer the disease, the harder it is to get an accurate diagnosis. This can then impact whether you receive the best treatment to address your specific case of kidney disease. AKF is committed to improving our understanding of rare diseases, from providing educational resources to continuing efforts related to our Unknown Causes of Kidney Disease (UCKD) Project.

One of those very rare kidney diseases is atypical hemolytic uremic syndrome (aHUS). September 24 is aHUS Awareness Day, an opportunity to shine a light on this serious kidney disease and the people who are living with it or caring for someone living with it. 

Here are 10 facts to help you understand this complex disease:

1. aHUS is a genetic disease that causes tiny blood clots to form in your blood vessels. These tiny clots make it harder for your blood to flow to your organs, including your kidneys. This can damage the kidneys or cause kidney failure. 
2. The aHUS Foundation estimates that fewer than 625 people in the United States of have been diagnosed with aHUS. You are more likely to get aHUS if you have a family history, such as a parent, grandparent or sibling with the disease.
3. While aHUS is caused by a genetic mutation, the mutation alone often does not cause the disease. Instead, the genetic mutation coupled with a "triggering" event activates the disease. Examples of triggering events include pregnancy, infections, cancer or certain medicines.
4. The three most common signs of aHUS are (1) kidney damage or kidney failure, (2) hemolytic anemia (which is a type of anemia in which red blood cells are destroyed at a rate faster than your body can replace them) and (3) thrombocytopenia (which means there are not enough platelets — blood cells that help your blood clot to stop bleeding — in your body). Most people with aHUS have all three of these signs, but it can vary from person to person.
5. aHUS is a form of thrombotic microangiopathy (TMA), a group of conditions that happens when these tiny blood clots form. In addition to aHUS, another common cause of TMA is thrombotic thrombocytopenic purpura (TTP), which causes blood clots from low activity of a protein called ADAMTS13. The low production of ADAMTS13 can either be caused by a genetic mutation or an autoimmune disorder. Other causes of TMA include infections, medicines, connective tissue diseases (like lupus), cancer, vasculitis, pregnancy, malignant hypertension, organ transplant and metabolic disorders.
6. Typical hemolytic uremic syndrome (HUS) also causes blood clots, but is a different disease. HUS is generally caused by a foodborne illness called E.coli-producing Shiga toxins (Stx HUS) and can cause diarrhea (often bloody), pain, cramping or bloating in the stomach area, fever and/or vomiting.
7. Diagnosing aHUS can be a challenging process as many other conditions can cause similar symptoms and aHUS affects everyone differently. Often, it requires a "diagnosis of exclusion," which means that doctors need to eliminate all the other possible options until aHUS is the only remaining possibility. This can make diagnosing the disease and receiving the proper treatment very difficult. 
8. Some of the tests a doctor may run to help determine if you have aHUS include a blood count (CBC), which measures your red blood cell and platelet counts, blood tests (like an eGFR test) to see how well your kidneys are working or a blood test to measure the level of ADAMTS13 in your blood to determine if it could be TTP. 
9. You may also undergo genetic testing to determine if you have one of the genetic mutations that can cause aHUS. However, 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.
10. There is no cure for aHUS, but it can be treated or managed. 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 or plasma therapy, which means exchanging a portion of your blood with fresh, healthy blood. If you reach kidney failure, you may also need to undergo dialysis treatments or have a kidney transplant. 

You can find out more about aHUS on AKF's website or on these websites:

• The aHUS Foundation
• aHUS Source
• The aHUS Alliance
• National Library of Medicine
• The National Organization for Rare Diseases