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Idiopathic Thrombocytopenic Purpuras.

Autoimmune in origin.
may occur in isolation or in association with an underlying condition such as lymphoma or collagen vascular disease like SLE.

Autoantibodies to platelets against platelet membrane glycoprotein IIb/IIIa, Major site of production of autoantibodies is spleen.

Acute - children (post infection)
Chronic - adults (increase in females, 20-40 yrs)

The spleen usually appears remarkably normal or mild enlargement.
No splenomegaly or lymphadenopathy.
Bone marrow aspiration – normocellular/increased numbers of megakaryocytes.

Diagnosis is by clinical picture, marrow examination, and exclusion of other causes of thrombocytopenia

In more than two thirds of patients, splenectomy is followed by the return of normal platelet counts and complete remission of the disease

Basic pathogenesis in TTP is widespread formation of hyaline thrombi in the microcirculation that are composed primarily of dense aggregates of platelets surrounded by fibrin.

Deficiency of enzymes - tissue metalloproteases that normally degrades very-high-molecular-weight von Willebrand factor (vWF), there is accumulation of vWF in plasma - promote platelet microaggregate formation throughout the microcirculation.

Formation of myriads of platelet aggregates causes thrombocytopenia, and the narrowing of blood vessels by the thrombi results in microangiopathic hemolytic anemia.

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