Atypical hemolytic uremic syndrome

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at December 8, 2016
StartDiseasesAtypical hemolytic uremic syndrome

Atypical hemolytic uremic syndrome (aHUS for short) is a very rare disease mostly affecting the kidneys. The disease is characterized by kidney problems, anemia, and blood clots. It is a serious and often life-threatening condition.


Definition & Facts

Atypical hemolytic uremic syndrome is a rare disease that destroys red blood cells and cause the kidneys to malfunction. Atypical hemolytic uremic syndrome is often a genetic disorder, although some people acquire it throughout the course of their lives as a result of underlying genetic factors and environmental factors or diseases.

Atypical hemolytic uremic syndrome can be chronic. It is a very serious illness that causes chronic kidney disease; in half of all cases, it results in end-stage renal disease. More adult women get aHUS than men because often it is triggered by pregnancy. It is believed that one in 500,000 Americans have this condition.

Atypical hemolytic uremic syndrome ought not be confused with typical hemolytic uremic syndrome which is caused by bacterial infection, specifically, an Escherichia coli infection. This condition causes diarrhea and affects children under the age of ten.

Symptoms & Complaints

The symptoms of aHUS are often triggered by the formation of blood clots which occur in the blood vessels of the kidneys. Those afflicted may experience vague feelings of fatigue, illness, and irritability that can be severe enough to warrant hospitalization.

The patient will have hemolytic anemia, a condition where red blood cells are being destroyed. They will also have thrombocytopenia, which means they have low levels of platelets.

They might also experience urinary abnormalities which could include darker urine and hematuria (blood in the urine). Their urine might be bubbly or frothy, which is an indicator that they are excreting a lot of protein (proteinuria).

People with aHUS will likely have high blood pressure (hypertension), and the patient might also have cardiovascular disease or experience a heart attack. They could have headaches, double vision, facial paralysis, seizures, stroke, or fall into a coma. They may experience gastrointestinal bleeding. It is also possible that they will have fluid in the lungs.


People with aHUS may have genetic mutations that causes their immune systems to respond differently than it should. About 30 percent of cases are associated with genetic mutations of the CFH gene. These mutations affect proteins that result in the body attacking healthy tissues, including the lining of the blood vessels in the kidneys.

The disease can be triggered by the body's response to an infection such as chickenpox or influenza. For women, pregnancy may be a trigger. Additional triggers may include HIV infection, organ transplants, stem cell transplants, autoimmune diseases, and select drugs and medications.

The cause of many cases of this disease cannot be determined, which is termed idiopathic aHUS. Usually there is no family history of the disorder among those who have this condition. It affects adults more than children.

Diagnosis & Tests

Atypical hemolytic uremic syndrome is very hard to diagnose in the early stages because often, there is no family history of any illness like this. The condition gets progressively worse and it is extremely important that the doctor recognizes it as soon as possible.

The doctor will run clinical urine tests to detect elevated levels of protein in the urine, and they will also run blood tests to check platelet levels. They may do an ultrasound to check on the kidney to see how severe the case is. It is possible they will order a magnetic resonance imaging (MRI) or a computed tomography (CT) scan depending on the symptoms.

Treatment & Therapy

Atypical hemolytic uremic syndrome is really rare and many believe that the best bet is to seek out a medical team that includes pediatricians, kidney specialists, and nutritionists. The patient will need support maintaining proper nutrition and will likely need intravenous feeding. It is possible the patient will need a blood transfusion. The doctor might give the patient vasodilators, drugs that help to control blood pressure.

Depending on how severe the case is, the patient may need dialysis. The belief is that the most effective therapy is a prescription of eculizumab, which has been proven to reverse kidney damage and stabilize platelet counts. Some people may lose kidney function and they will need a kidney transplant.

Prevention & Prophylaxis

In many cases, there is no way to prevent aHUS because it is the result of a complex interaction of genetic factors and environmental factors. To the extent that viral infections or bacterial infections are associated with an increased risk of this disease, obtaining vaccinations may help prevent the onset of this condition.