الفهرس 
NTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Thrombotic thrombocytopenic purpura (TTP) is a rare life threatening condition characterized by extensive thrombi formation which are mainly formed of platelets and very rich in von Willebrand factor (VWF).
TTP affects most commonly terminal arterioles and capillaries of large number of organs such as the kidney, pancreas, spleen, heart, brain and adrenal gland. TTP is mostly accompanied with low platelet count and microangiopathic hemolytic anemia.
TTP pathogenesis arises from the deficiency in ADAMTS-13 (a disintegrin and metalloprotease with thrombospondin 1 repeats); which acts as VWF-cleaving protease. ADAMTS13 cleaves plasma VWF multimers at the A2 domain at the Y1605-M1606 peptidyl bond, which will prevent the microthrombus formation caused by UL-VWF.
Deficiency of ADAMTS-13 will lead to persistence of ultra-large VWF (ULVWF) multimers mainly in microcirculation. These ULVWF multimers attract platelets to induce platelet thrombi formation. Consequently, extensive multi thrombi and severe organ damage follow.
The autoimmune form of TTP is also called idiopathic TTP. Anti ADAMTS-13 antibodies are usually detected in the TTP patient plasma with frequent reduction of ADAMTS13 activity to <5%.
Deficiency of ADAMTS-13 in acquired cases of TTP is due to neutralizing anti ADAMTS- 13 antibodies leading to marked decrease in ADAMTS-13 proteolytic activity. Acquired TTP is associated with IgG antibodies to ADAMTS-13 with few cases due to IgM and IgA antibodies.