Atypical Hemolytic Uremic Syndrome

Written by Rachel Reiff Ellis
Medically Reviewed by Neha Pathak, MD on October 04, 2024
9 min read

Atypical hemolytic uremic syndrome (aHUS) is a disease that causes blood clots in small blood vessels in your kidneys and other organs. These clots keep blood from getting to your kidneys, which can lead to serious medical problems, including kidney failure. There's no cure, but treatment can help manage the condition.

Atypical vs. typical hemolytic uremic syndrome

Atypical hemolytic syndrome is different from "typical" hemolytic uremic syndrome but can cause similar problems. It is classically due to certain bacteria that can cause diarrhea including E. coli and shigella.

You can get aHUS at any age. In kids, an equal number of boys and girls get it. Later in life, more women than men tend to get it because pregnancy can be a trigger for the disease.
Atypical hemolytic uremic syndrome is rare. Experts don't know exactly how many people have it, but some studies say it affects only 2 people out of every million in the U.S.

Most aHUS cases happen because of a change called a mutation in a gene. The mutation itself isn't enough to cause the disease. The disease symptoms start after certain things trigger them, such as:

  • Pregnancy
  • Infection
  • Cancer
  • Certain medications
  • Organ transplant
  • Certain chronic diseases, such as systemic sclerosis or malignant hypertension

Up to half of people with aHUS don't have a gene mutation doctors can find. This type of aHUS is called "idiopathic," meaning the cause is unknown. Researchers think these cases of aHUS are due to gene mutations they haven't been able to identify.

Symptoms of aHUS typically come on suddenly after a trigger. These flare-ups can be mild or severe. Mild flare-ups may not affect your kidneys, but severe ones can cause kidney failure.

Some of the symptoms you may have in the early stages of aHUS include:

  • Weakness and a lack of energy
  • General feeling of being sick

The disease is "progressive," which means the symptoms will get worse over time, especially if your doctor isn't able to diagnose it during the early stage.

The main organs affected when you have aHUS are your kidneys. But blocked blood flow can also damage other organs in your body such as your brain, liver, lungs, and heart.

Diagnosing aHUS can be tricky if you don't have a family history of the disease. A nephrologist (kidney doctor) or hematologist (blood doctor) will be most likely to know about aHUS. They'll look for these signs: 

  • Hemolytic anemia
  • Low count of platelets (blood cells that help with clotting)
  • Kidney problems

Tests for atypical hemolytic uremic syndrome

Your doctor can order tests to help figure out if you have aHUS. These include:

  • Complete blood count (CBC). Your doctor will likely take a blood sample to get a complete blood count, or CBC. This measures your platelet and red blood cell levels.
  • Estimated glomerular filtration rate (eGFR). Your doctor may check how well your kidneys are working with a routine test called estimated glomerular filtration rate, or eGFR. This measures the levels of creatinine (a waste product) in your blood. 
  • Test for ADAMTS13. Because aHUS can look a lot like a condition called thrombotic thrombocytopenic purpura (TTP), your doctor will also test your blood for a specific protein called ADAMTS13. If your levels are low, you have TTP instead of aHUS.
  • Genetic testing. Looking at your genes can also help your doctor figure out if you have aHUS. But a genetic test won't always show aHUS because researchers haven't identified all the genes involved with the disease. 

To be sure you get the most out of a doctor visit, write down your symptoms and a list of questions you want to ask. It's helpful to have a loved one with you to help you understand the information your doctor gives you.

You can ask:

  • What is the best treatment for me?
  • What are the goals of treatment?
  • Will my treatment have any side effects?
  • Should I have a genetic test?
  • Should I see a specialist?
  • Are there any clinical trials I could be a part of?

Although you may start with your primary care doctor as you have symptoms, aHUS is often diagnosed and treated by specialists, including a: 

  • Nephrologist. A nephrologist is a doctor who specializes in kidney conditions and kidney diseases. They may be the doctor who diagnoses your aHUS and also your primary point of contact for your aHUS care.
  • Hematologist. A hematologist specializes in blood-related conditions.

Typically your nephrologist and hematologist will work together on a treatment plan for you. 

The FDA has approved two drugs to treat aHUS:

Both drugs are monoclonal antibodies. These are human-made proteins that act like natural antibody proteins in your body. They attach to other proteins called antigens. Once they attach, they tell your immune system to destroy cells with that antigen.

Eculizumab can increase your blood platelet and red blood cell counts. If you take it early enough, it can also reverse any kidney damage you have.

Your doctor will give you eculizumab by injection in their office. You may have side effects from the drug, including:

  • Headache
  • Irritated nose or throat
  • Cold or flu-like symptoms
  • Back pain
  • Constipation
  • Nausea, diarrhea, or stomach pain
  • Feeling dizzy, tired, or weak
  • Trouble sleeping
  • Muscle or joint pain
  • Arm or leg pain
  • Muscle spasms
  • Hair loss

You can also get ravulizumab as an injection. Common side effects include high blood pressure, headache, and cold symptoms. You could also have digestive system problems such as diarrhea, nausea, and vomiting.

Eculizumab and ravulizumab belong to a class of drugs called complement inhibitors. These drugs may carry a risk of getting meningococcal disease. The CDC suggests people taking them get a meningococcal vaccine. Your doctor may also suggest you take antibiotics to help prevent meningococcal disease.

Besides eculizumab and ravulizumab, you can also treat the symptoms of aHUS with plasma therapy. Plasma is the liquid portion of your blood that takes important nutrients, hormones, and proteins throughout your body.

When you get plasma therapy, you may either have a plasma infusion or plasma exchange. In a plasma infusion, a doctor puts plasma from a donor into your body. In a plasma exchange, a doctor filters plasma out of your blood and replaces it with donor plasma.

If your kidneys don't respond to treatment, you may need kidney dialysis or a kidney transplant.

Besides kidney failure, complications from aHUS are common and include:

  • Hemolytic anemia (red blood cells dying faster than you can make them)
  • Thrombocytopenia (low blood platelet count)
  • Kidney damage or failure
  • High blood pressure
  • Heart disease or heart attack
  • Headaches
  • Double vision
  • Facial paralysis
  • Seizures

You need emergency room care if you have severe symptoms such as:

  • Peeing very little
  • Confusion or altered mental state
  • Severe swelling
  • Difficulty breathing

Some people who have aHUS have one flare-up. Others have regular flare-ups that can be serious. When you're diagnosed, you may need to stay in the hospital for some time.

Although aHUS is a lifelong condition, with early treatment you can manage the effects. Stay in contact with your doctors so they can monitor your health and keep you on track with therapies and symptom management.

It’s common to deal with difficult emotions when you live with a chronic kidney disease. The more advanced your disease is or severe your symptoms are, the more impact your disease will have on your mental health.

There are steps you can take to care for your emotional well-being as you live with aHUS. 

  • Seek out social workers. Social workers are a good resource for helping you navigate not only the logistical side of living with a chronic kidney disease but can also help connect you with emotional support. 
  • Connect with a counselor. Talk therapy with a licensed counselor or therapist can help relieve some of your emotional burden and teach you tools for managing your mental health. 
  • Care for your overall health. Get good sleep and find ways to reduce your stress levels. Eat a kidney-friendly diet and try to move your body every day. Feeling as well as you can in other aspects will help your overall mood.

It's helpful to talk to family and friends to get the emotional backing you may need as you manage your condition. You can also ask your doctor about how to join a support group, where you'll get to talk to other people with aHUS who understand what you're going through.

There are several organizations you can connect with to find information, the latest research, and others dealing with aHUS and other rare diseases. Often these groups have opportunities to get involved as a patient advocate, which can help doctors develop better treatments.

Resources include:

  • Organizations specifically centered on aHUS such as aHUS Alliance and the Atypical HUS Foundation
  • Kidney-focused organizations such as the American Association of Kidney Patients, American Kidney Fund, and National Kidney Foundation
  • Rare disease organizations such as the Genetic and Rare Diseases Information Center and the National Organization for Rare Disorders

Medication alone for aHUS can cost up to $55,000 a year. Combined with the costs of hospital stays and doctor visits, treatment for the disease can be costly, even if you have health insurance. 

There are organizations that can help. 

The National Organization for Rare Diseases (NORD)’s Atypical Hemolytic Uremic Syndrome (aHUS) Patient Assistance Program offers assistance to people with the disease. They help with insurance premiums and copays, diagnostic tests and travel assistance for clinical trials, or meeting with disease specialists.

The Assistance Fund helps people with little to no health insurance get access to treatment with financial assistance and advocacy. 

Good Days is a national nonprofit organization that helps with financial resources for lifesaving and life-extending treatments to people who need them. 

Since aHUS is a disease you inherit through your genes, you can’t prevent it. With treatment and lifestyle management, you can help control symptoms and prevent organ damage or other complications.

Atypical hemolytic uremic syndrome (aHUS) is a condition often caused by a genetic mutation plus environmental triggers such as pregnancy, cancer, or infection. It causes small blood clots in your kidneys and other organs. It can cause anemia, low platelets, and kidney failure. Two FDA-approved monoclonal antibody drugs treat it.

What is the survival rate for HUS?

Your life expectancy when you have aHUS depends on several factors, including your age at diagnosis, how well you follow your treatment plan, and your overall health. Within a year of diagnosis, over half of people with aHUS will need dialysis or will have irreversible kidney damage. Death rates are as high as 25%. Most people progress to end-stage kidney failure within 3 years. 

How long can you live with aHUS?

Even though there isn’t a cure for aHUS, with early diagnosis and proper treatment you can manage the disease. Although 50% of people with aHUS progressed to end-stage kidney disease in past years, current medications are helping reduce this rate and improve life expectancy. 

Which drugs cause hemolytic uremic syndrome?

Certain drugs can trigger the disease in people with the mutation, including quinine (a malaria medication), some cancer medications, some immunotherapy drugs such as cyclosporine and interferon, drugs that prevent blood clots, and some oral birth control medications.  

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