HUS is disease that can affect multiple body organs and manifests primarily as kidney failure, hemolysis (destruction of red blood cells) and low platelet count; however other organs can be involved.


HUS has two main types:


1-Typical HUS:


Seen mainly in children and it is caused by certain strains of bacteria (Shiga toxin-producing E. Coli) that cause diarrheal disease that is usually bloody.


2-Atypical HUS:


It is primarily caused by mutations in the complement factors or proteins that regulate their activities. Complement system consists of large numbers of proteins that are present in the plasma and on cell membrane surfaces. It plays an important role in the immune system. Since uncontrolled activation of complement proteins can be harmful, presence of a regulatory mechanism to control their activity is essential. Inherited mutations of one or more components of this system, or in some patients, development of antibodies that can inhibit their function, can lead to uncontrolled and damaging activity, causing damage to the lining of the small blood vessels in certain body organs, which can lead to development of clots and destruction of the red blood cells within those vessels.


Diagnosis depends on the clinical presentation and typical abnormalities in the laboratory tests, however, it is important to differentiate this disorder from another disease called thrombotic thrombocytopenic purpura (TTP), which can have a similar presentation. This can be done by measuring an enzyme in the blood called ADAMTS13. The presence of adequate level of this enzyme, confirms the diagnosis of atypical HUS. This differentiation has therapeutic implications, since the treatment of TTP is based on Plasma exchange/infusion, while many authorities in the field believe that a drug called Eculizumab, which inhibit the complement system, is the best therapeutic option for atypical HUS. 




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Hemolytic Uremic Syndrome (HUS)