Summary of 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.

Causes
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.

Clinical Features
Signs and symptoms of ITP common to all forms of thrombocytopenia include petechiae, ecchymoses, and mucosal bleeding from the mouth, nose, and GI tract. Generally, hemorrhage is a rare physical finding. Purpuric lesions may occur in vital organs, such as the lungs, kidneys, or brain, and may prove fatal.
With acute ITP, which is common in children, onset is usually sudden and without warning, causing easy bruising, epistaxis, and bleeding gums. Onset of chronic ITP is insidious.

Diagnosis
Platelet count less than 20,000/µl combined with prolonged bleeding time suggest ITP. Platelet size and morphologic appearance may be abnormal; anemia may be present if bleeding has occurred.
As in thrombocytopenia, bone marrow studies show an abundance of megakaryocytes and a shortened circulating platelet survival time (hours or days). Occasionally, platelet antibodies may be found in vitro, but this diagnosis is usually inferred from platelet survival data and the absence of an underlying disease. The patient’s immunoglobulin G level may also be increased.

Treatment
Acute ITP may be allowed to run its course without intervention or may be treated with a glucocorticoid or immune globulin. 

For chronic ITP, a corticosteroid may be the initial treatment of choice. Patients who fail to respond within 1 to 4 months or who need high steroid dosage are candidates for splenectomy, which has an 85% success rate. Alternative treatments include immunosuppression, high-dose I.V. gamma globulin, and immunoabsorption apheresis using staphylococcal protein-A columns.
The patient may find complementary therapies to be helpful. He may explore such therapies with his physician.

Prognosis
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.