HUS vs. Atypical HUS

Atypical HUS vs. HUS | Information for Parents

When Doctors first diagnosed you or your child, they looked at the symptoms, and based on the early symptoms, may have classified your child has having either “HUS” or “Atypical HUS”. HUS , may also be known as “regular” or “Diarrhea”. HUS is caused by an external agent, usually a bacteria, and is obtained by usually eating contaminated food. Atypical HUS has quite a few symptoms that are close to “HUS”. Years ago, these two diseases may have been confused and misdiagnosed.

Atypical HUS is not caused by an external agent (such as a bacteria, virus etc). Instead, the body’s innate immune system sets off an internal chain of events that ends us causing problems. So really, the disease is caused by the body’s immune system's inappropriate response.

So the question then becomes, why does the body not respond properly? The answer, in short , is that the origin of the improper response is due to genetics. The good news is: We have identified a host of genes that are definitely linked to the disease. We also have cases that the known genes are not present. In other cases, the disease appears out of nowhere. Some Doctors may use the term "idiopathic" cause. Idiopathic causes are believed to originate from a mutated gene. There are a variety of other rare Atypical causes, such as HIV and Pregnancy induced HUS.

This chart is general in nature, and is not an exact diagnostic tool, but rather an overall summary:

Caused by a Bacteria or Virus No Yes
Initial Symptoms are severe No Yes
Accompanied by Severe Diarrhea No Yes
Dialysis often needed Yes Yes
Blood Pressure Regulation Problems Yes Yes
Temporary Kidney Failure is Common Yes Yes
Permanent Kidney Failure is Common Yes No in most cases
Disease is often Recurring Yes No
Complications throughout life may occur Yes No
Genetic Problem is root cause Yes No

As we can see, the Atypical form is subject to longer lingering effects, and is much more likely to become a chronic problem. Recurring episodes are much more common with the Atypical form of the disease. Atypical cases frequently start out with flu-like symptoms that do not go away. Eventually, the lethargic behavior results in loss of appetite, and often kidney function may already be affected.