Idiopathic Thrombocytopenic Purpura
Thrombocytopenia that results from immunologic platelet destruction is known as idiopathic thrombocytopenic purpura (lTP). This form of thrombocytopenia may be acute (postviral thrombocytopenia) or chronic (Werlhof's disease, purpura hemorrhagica, essential thrombocytopenia, or autoimmune thrombocytopenia). The acute form usually affects children between ages 2 and 6; the chronic form mainly affects adults under age 50, especially women between ages 20 and 40.
Purpura refers to a purplish or reddish-brown skin rash caused by the leakage of blood from broken capillaries into the skin. Other names for ITP include purpura hemorrhagica and essential thrombocytopenia.
ITP is an autoimmune disorder. 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. The acute form usually follows a viral infection, such as rubella and chickenpox, and can result from immunization with a live vaccine. The chronic form seldom follows infection and is commonly linked with other immunologic disorders, such as systemic lupus erythematosus.
Human immunodeficiency virus (HIV) infection has become a common cause of ITP and should be considered in the differential diagnosis. ITP can be the initial symptom of HIV infection - a symptom indicating AIDS-related complex or a complication of fully developed AIDS. It's also often a precursor to lymphoma.
In addition to a complete medical history and physical examination, diagnostic procedures for idiopathic thrombocytopenic purpura may include the following:
Sometimes, a bone marrow aspiration is performed to look at the production of platelets and to rule out any abnormal cells the marrow may be producing that could lower platelet counts.
Acute ITP may be allowed to run its course without intervention, or it may be treated with glucocorticoids or immune globulin. Treatment with plasmapheresis or plateletpheresis with transfusion has been attempted with limited success.
For chronic ITP, corticosteroids are the treatment of choice to suppress phagocytic activity, promote capillary integrity, and enhance platelet production. Patients who fail to respond spontaneously within 1 to 4 months or who require high doses of corticosteroids to maintain platelet counts require splenectomy,
Splenectomy may be up to 85% successful in adults when splenomegaly accompanies the initial thrombocytopenia. Before splenectomy, the patient may require blood, blood components, and vitamin K to correct anemia and coagulation defects. After splenectomy, she may need blood and component replacement and platelet concentrate. Normally, platelets multiply spontaneously after splenectomy.
Alternative treatments include immunosuppressants (cytoxan or vincristine sulfate, for example) and highdose I.V. immune globulin in adults (85% effective).
The use of immunosuppressants requires weighing the risks against the benefits. Immune globulin treatment has a rapid effect, raising platelet counts within 1 to 5 days, but the beneficial effect lasts only 1 to 2 weeks. Immune globulin is usually administered to prepare severely thrombocytic patients for emergency surgery.
The causes and risk factors are unknown (except in children when it may be related to a viral infection), and prevention is unknown.
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