aHUS presents with variable symptoms. The initial onset can appear to be flu-like, with lethargic behaviour, pale skin tone, and loss of appetite. Because aHUS is so rare, many doctors may have never encountered it. As well, signs and indicators are similar to other illnesses. For these reasons, it is difficult to diagnose.
Doctors and their health care team must, therefore, look at many factors when making a diagnosis- including, clinical symptoms, lab findings, and results from more specialized tests such as gene analysis.
Symptoms of aHUS most often include:
- nausea and vomiting
- shortness of breath (dyspnea)
- anemia (low red blood cell/platelet count in the blood)
- thrombocytopenia (low platelet count in the blood)
- kidney (renal) symptoms, including kidney damage, kidney failure or end-stage renal disease (i.e. damage requiring chronic dialysis)
The symptoms described above may continue to worsen during active episodes or attacks.
In some cases, severe, non-kidney related symptoms present themselves right away, and in others, symptoms do not occur until later. Symptoms can include:
- gastrointestinal problems including severe stomach pain
- inflamed colon
- blood vessel damage
- heart attacks
- neurological issues including seizures
Patients with aHUS, whether at initial onset or during recurring episodes usually experience symptoms because of some sort of major event that occurs elsewhere in the system. For that reason, during an active episode of aHUS, there are tell-tale signs that are more obvious, which can be detected from the following lab findings:
- Platelets: decreased levels (may fall below 125 x 109/L) when normal levels should be 150-400 x 109/L)
- Hemoglobin: decreased levels (may fall to 60-70 g/L, when normal levels should be 120-153 g/L)
- Haptoglobin: decreased levels
- Lactate Dehydrogenase (LDH): elevated levels
- Creatinine: elevated levels (indicative of declining kidney function)
- BUN (blood urea nitrogen): elevated levels (indicative of declining kidney function)
In about half of patients, testing for mutations in complement genes (i.e. that produce proteins which control the activity of the complement system) can confirm a diagnosis of aHUS. In addition to gene testing, doctors can also test for the presence of proteins called autoantibodies, which have the same effect on the activity of the complement system as a mutation.