aHUS atypical Hemolytic Uremic Syndrome (aHUS) website

What is aHUS?

What causes aHUS?

aHUS is caused by a change, or mutation, in a person’s genes. However, as several different genes can be involved, the absence of an identified genetic mutation does not rule out aHUS1


aHUS results from changes, or mutations in the genes that produce proteins that help control the complement system which is part of your body’s natural immune defense system.1

When the complement system is uncontrolled, it can attack the body it normally protects.2 As a result, aHUS can do great damage to vital organs if it is left undiagnosed and untreated.2

Although aHUS is a genetic disease, 30% to 50% of people with aHUS will not have genetic mutations that can be identified through genetic tests.3,4

Testing for specific genes is not necessary for your doctor to diagnose you with aHUS. The absence of genetic mutation does not rule out aHUS.1

Because aHUS can be caused by a genetic mutation, it is known as a chronic disease. The underlying cause of the disease is always present and the risk of sudden, damaging symptoms is constant.1,5