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The antigen usually forms immune complexes with circulating antibody, and it is thought that theimmune complexes bind to Fc receptors in the platelets, leading to destruction of the spleen. Usually resolves when antigen is removed.Chronic ITP: more common in adults, gets progressively worse.Antibodies are generally of the IgG class, although IgA and IgM are also identified. They react against one or more of several platelet glycoproteins (GPIIb-IIIa, GPIb-IX, GPIa-IIa). The body-coated platelets are removed from the circulation by mononuclear phagocytes in the spleen through the Fc receptor. A variant of neonatal thrombocytopenia occurs when the mother does not have ITP, but makes IgG antibodies against the antigen inherited from the father and found on fetal platelets but not on maternal platelets. The most common antibody in this condition is against the human platelet antigen-a antigen on the GPIIIa protein.AdherenceThrombotic Thrombocytopenia PurpuraCharacterized by thrombotic microangiopathy in which platelets aggregate and cause occlusion of arterioles and capillaries within the microcirculation. Aggregation may lead to increased platelet consumption and organ ischemia. Platelet aggregation and microthrombi formation are found throughout the entire vascular system, causing damage to multiple organs (kidneys, brain, heart, pancreas, spleen, adrenal glands). The thrombi are primarily composed of platelets with minimal fibrin and red cells, differentiating them from thrombi secondary to intravascular coagulation. Most cases are related to a dysfunction of the plasma metalloprotease