الفهرس 
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Abstract
The ADAMTS13 gene provides instructions for making an enzyme that is involved in blood clotting. After an injury, clots normally protect the body by sealing off damaged blood vessels and preventing further blood loss.
The ADAMTS13 enzyme processes a large protein called von Willebrand factor, which also plays a role in clot formation. The unprocessed form of von Willebrand factor interacts easily with cell fragments called platelets, which circulate in the bloodstream and are essential for blood clotting. The factor helps platelets stick together and adhere to the walls of blood vessels, forming temporary clots. The ADAMTS13 enzyme cuts von Willebrand factor into smaller pieces. By processing von Willebrand factor in this way, the enzyme prevents it from triggering the formation of unnecessary blood clots.
A severe deficiency in von Willebrand factor-cleaving protease (ADAMTS13) activity (< 5% that in normal plasma) has been observed in most patients with a diagnosis of thrombotic thrombocytopenic purpura (TTP) but not in those with a diagnosis of hemolytic uremic syndrome. However, ADAMTS13 deficiency has been claimed not to be specific for TTP, since it was observed in various thrombocytopenic disorders as severe sepsis or septic shock, heparin-induced thrombocytopenia, idiopathic thrombocytopenic purpura ,or other hematologic,or miscellaneous conditions.
TTP was originally characterized by a pentad of thrombocytopenia, MAHA, fluctuating neurological signs, Renal impairment and fever.
often with insidious onset. However, TTP can present without the full pentad; up to 35% of patients do not have neurological signs at presentation and renal abnormalities and fever are not prominent features. The revised diagnostic criteria state that TTP must be considered in the presence of thrombocytopenia and MAHA alone. This can result in an increased referral of other TMAs .
ADAMTS13 activity may be involved not only in sinusoidal microcirculatory disturbances, but also subsequent progression of liver injuries, eventually leading to multiorgan failure. This concept can be applied to the development or aggravation of liver diseases, including liver cirrhosis, alcoholic hepatitis, veno-occlusive disease, and adverse events after liver transplantation.