Diagnosis
aHUS is not the only condition that causes systemic TMA, a fact that makes differential diagnosis essential. Historically, the clinical diagnosis of TMA-causing diseases was grouped into a broad category that (in addition to aHUS) included thrombotic thrombocytopenic purpura (TTP) and Shiga-toxin-producing Escherichia coli hemolytic uremic syndrome (STEC-HUS). However, it is now understood that although aHUS, STEC-HUS, and TTP have similar clinical presentations, they have distinct causes and specific tests can be conducted to differentiate these diseases. In addition, there are other conditions that can cause TMA as a secondary manifestation; these entities include systemic lupus erythematosus (SLE), malignant hypertension, progressive systemic sclerosis (PSS, also known as scleroderma), the pregnancy-associated HELLP (hemolysis, liver dysfunction, and low platelets) syndrome, and toxic drug reaction (e.g., to cocaine, cyclosporine, or tacrolimus). Nevertheless, aHUS should be suspected in patients presenting with systemic TMA, and appropriate diagnostic work-up should be undertaken.The neurological and kidney-related signs and symptoms of aHUS overlap with those of TTP. However, unlike aHUS, TTP is primarily an autoimmune disorder in which the presence of an inhibitory autoantibody results in severe deficiency of ADAMTS13, an enzyme that cleaves von Willebrand factor (vWf), a large protein involved in blood clotting, into smaller pieces. (TTP also can be a genetic disorder characterized by mutations in the ADAMTS13 gene leading to severe ADAMTS13 deficiency. This congenital cause of ADAMTS13 deficiency is called Upshaw-Schülman syndrome.) A lab test showing ADAMTS13 activity levels of ≤5% is indicative of TTP.Similarly, the gastrointestinal (GI) signs and symptoms of aHUS overlap with those of STEC-HUS.
Combined liver-kidney transplantation has been attempted in patients with aHUS, although this high-risk procedure has a mortality rate approaching 50%.Prior to availability and usage of the treatments,  quality of life was very poor for patients with aHUS; burdened with fatigue, renal complications, hypertension, neurological impairment, gastrointestinal distress, clotting at the site of venous access, and in worst cases, death. PE/PI is also reported to be associated with significant safety risks and is highly disruptive to patients lives due to the requirements for extensive vascular access and frequent administration.Since the approval of eculizumab (Soliris) the prognosis for aHUS patients has improved greatly. Risk of relapse is present after discontinuation of eculizumab treatment and close monitoring is required. Epidemiology
aHUS can be inherited or acquired, and does not appear to vary by race, gender, or geographic area. As expected with an ultra-rare disease, data on the prevalence of aHUS are extremely limited. A pediatric prevalence of 3.3 cases per million population is documented in one publication of a European hemolytic uremic syndrome (HUS) registry involving 167 pediatric patients. Society and culture
Naming
Atypical hemolytic uremic syndrome (aHUS) has also been referred to as diarrhea-negative hemolytic-uremic syndrome (D− HUS). : 2170

Research directions
Patient advocacy groups have been helping to determine research priorities. References


== External links ==