Most of the time, atypical HUS does not present with initial severe symptoms. The initial onset will most likely appear to be flu like, with lethargic behavior, pale color and a loss of appetite. It has been our experience that adult hospitals may often send the patient home with a flu diagnosis, while children’s hospitals may do a blood draw and conduct basic tests, such as Hemoglobin, Hematocrit, white blood cell counts, and platelet counts.

After initial blood tests, the hospital may conduct Creatinine and BUN tests and may (or may not) reach an initial Diagnosis of atypical HUS. The flu like symptoms described above will continue to worsen when episodes are active. At this point, kidney function may begin to fall, often quite dramatically. Other organs sometime experience problems in some cases. Quite often, seizures have been reported, along with other neurological issues. Sometimes gastronomical problems occur as well.

During an extended atypical attack or episode, the tell-tale signs of aHUS are very obvious. Hemoglobin levels may fall to 6-7, when normal levels should be 11-13: Hematocrit levels may fall in the low 20s, when normal levels should be in the mid 30s. Creatinine and BUN levels start to rise, characteristics of failing kidney function. Blood Pressure will become a nagging, recurring problem. Diarrhea and vomiting may also be present (sometimes that occurs with the initial onset, at other times it occurs later).

Specific Testing

Doctors can perform certain tests to help diagnose HUS and aHUS. Both HUS and aHUS share some signs and symptoms with another disease called thrombotic thrombocytopenic purpura (TTP), which has a different underlying cause. Doctors can measure levels of a certain protein in the blood, ADAMTS13, which may help clarify whether a patient has aHUS or TTP. The physician will need to rely on signs, symptoms, lab tests, and frequent visits to determine care and treatment for patients suspected of any of these potentially life-threatening diseases.

Genetic Testing

When a patient becomes stable, his or her doctor may send blood samples for genetic testing to a specialized lab. In America, the primary genetic testing facility for aHUS patients is at the University of Iowa. Under the direction of Dr. Richard Smith, Molecular Otolaryngology Research Laboratories (MORL) staff currently does the most comprehensive genetic testing available for this disease. One or more genetic abnormalities may be discovered through genetic testing, although about 50% of aHUS screening results come back as being of unknown cause (idiopathic). Since genetics is a rapidly changing field, we strongly suggest that you monitor aHUS advancements on a regular basis.


These can include stroke, seizures, severe stomach pain, inflamed colon, blood vessel damage and heart attacks. Patients who have recurring episodes will usually experience some sort of major event that occurs elsewhere in the system.


It is important not to confuse “triggers” of atypical HUS with the root cause. In normal life, many of us get colds, the flu, infections, and the body’s immune system deal with those properly. In aHUS, a person may get a cold, and it triggers a full blown aHUS episode. This occurs simply because the body’s immune system is not reacting properly to the event.