Idiopathic thrombocytopenic purpura
Idiopathic thrombocytopenic purpura (ITP), thrombocytopenia that results from immunologic platelet destruction, may be acute (postviral thrombocytopenia) or chronic (Werlhof’s disease, purpura hemorrhagica, essential thrombocytopenia, autoimmune thrombocytopenia). Acute ITP usually affects children between ages 2 and 6; chronic ITP mainly affects adults younger than age 50, especially women between ages 20 and 40.
The prognosis for acute ITP is excellent; nearly four out of five patients recover without treatment. The prognosis for chronic ITP is good; remissions lasting weeks or years are common, especially among women.
ITP may be an autoimmune disorder because antibodies that reduce the life span of platelets have been found in nearly all patients. The spleen probably helps to remove platelets modified by the antibody. Acute ITP usually follows a viral infection, such as rubella and chickenpox, and can follow immunization with a live virus vaccine. Chronic ITP seldom follows infection and is commonly linked to immunologic disorders, such as systemic lupus erythematosus or human immunodeficiency virus infection. It’s also linked to drug reactions.