5 Main Symptoms of aHUS

Brian Murphy, Ph.D. avatar

by Brian Murphy, Ph.D. |

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aHUS symptoms

In atypical hemolytic uremic syndrome (aHUS), an overactive immune system mistakenly attacks the lining of blood vessels. This triggers inflammation and leads to the formation of blood clots, especially in the small blood vessels. The blood clots can damage various organs, especially the kidneys, and cause red blood cells to burst when the cells try to squeeze past the clots, leading to anemia.

People with aHUS may also have thrombocytopenia or low levels of platelets since many of the platelets in the body become involved in the formation of the blood clots. All these can lead to a variety of different symptoms.

The five most common symptoms include:


Anemia can lead to fatigue, a chronic state of exhaustion that doesn’t go away with rest. When there is a lack of red blood cells, the body cannot deliver enough oxygen to all the tissues, negatively affecting their function.

Also contributing to fatigue is a buildup of toxins in the blood due to damage to the kidneys.

Shortness of breath

Anemia can lead to shortness of breath because there aren’t enough red blood cells that carry oxygen in the body. This can cause patients to feel like they cannot catch their breath or even feel like they are suffocating.

Small clots in the blood vessels that go to the lungs, as well as a buildup of toxins in the blood from kidney damage, can also cause shortness of breath.


The abnormal blood clots in aHUS can affect blood vessels in other organs besides the kidneys. When they affect the vessels that supply blood to the brain, it can cause small areas of the brain to receive insufficient oxygen and nutrients. This can affect a person’s ability to think, leading to confusion.

Higher levels of toxins in the blood from kidney damage can also interfere with the ability of the brain to function and lead to confusion.

Nausea and vomiting

Nausea and vomiting are other common symptoms of aHUS.

The buildup of toxins from kidney failure can be one factor leading to nausea and vomiting.

Damage to the autonomic nervous system from blood clots or the buildup of toxins can cause abnormal activity of the stomach and intestines, leading to nausea and vomiting. (The autonomic nervous system regulates bodily functions such as digestion, breathing rate, and urination.)

High blood pressure

Patients with aHUS may also commonly experience high blood pressure. Damage to the kidneys can interfere with their ability to clear waste out of the blood. This means there is less fluid being excreted as urine. When too much liquid is in the blood, it can cause an increase in pressure on the vessel walls. Blood clots in blood vessels can also result in increased pressure on the blood vessels since the clots slow down or prevent blood flow. High blood pressure can lead to headaches and even seizures.


Last updated: Dec. 21, 2020


aHUS News is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.