The SHUa is a disease that arises from the disbalance in the alternative pathway of the complement system – one of the systems of defense of our body against infections. Although it is genetic, the SHUa can occur at any age once other factors, such as an infection, use of certain medications, surgeries, and coexisting conditions (cancer, systemic lupus erythematosus, arterial hypertension and others) contribute to the appearance of the manifestations.