Idiopathic thrombocytopenic purpura, which is also called ITP, is an autoimmune disorder that causes very low platelet counts. An autoimmune disorder is one in which a person produces antibodies against his or her own tissues.
Platelets, which are made by the bone marrow, are essential for blood clotting. In ITP, the body produces antibodies that attack the platelets and destroy them. Normally the body makes antibodies to fight infections. In ITP, the body for some reason makes antibodies against its own tissues, called autoantibodies. These autoantibodies act to destroy platelets. The result is a low platelet count, known as thrombocytopenia.
The cause of ITP is unknown. But certain viral infections seem to cause some cases of ITP. This in turn creates antibodies that attack the platelets, which are then removed from the bloodstream. Normal platelet counts are between 150,000 and 450,000. People with ITP may have very low platelet counts, often lower than 20,000 to 50,000.
Viral infection is believed to be one of the things that causes the body to make antibodies against platelets. A recent immunization using a live virus is also associated with an increased risk of ITP. ITP is twice as common in females as in males. The disease is most common in adults who are 20 to 50 years of age and in children who are 2 to 9 years of age. ITP is more likely to cause bleeding in older individuals or people who have had bleeding problems in the past.
New research findings suggest that autoimmune disorders may be triggered by a transfer of cells between the fetus and the mother during pregnancy. The study involved women with scleroderma, an autoimmune disorder involving the skin. These women have more fetal cells in their blood decades after a pregnancy than women who don't have scleroderma. While further research is needed to substantiate these findings, the study does offer an explanation for the much higher incidence of autoimmune disorders in women than in men.
Usually there are no signs or symptoms of ITP until the platelet count becomes quite low. The viral infection that precedes some cases of ITP may be an ordinary one, even a simple upper respiratory infection.
If the platelet count falls to an extremely low level, spontaneous bleeding may occur. This bleeding may occur at any site in the body. Usually it starts as easy bruising and bleeding from the gums. A more severe form is gastrointernal bleeding, which can occur in the vital organs in the stomach area. Intracerebral hemorrhage, or bleeding into the brain, can cause a stroke.
ITP is diagnosed based on symptoms and results of blood tests. A complete blood count, or CBC, identifies low platelet counts. The blood can also be tested for platelet autoantibodies to confirm the diagnosis.
If the blood tests do not confirm the diagnosis, a bone marrow biopsy can be performed. During a bone marrow biopsy, a sample of bone marrow is taken from the body and studied. The bone marrow sample should show normal bone marrow and normal amounts of cells that develop into platelets. Because ITP involves platelet destruction in the bloodstream, the results of the bone-marrow tests should remain normal.
There is no known prevention for ITP.
Most cases of ITP do resolve. However, some people develop chronic ITP. They may have prolonged episodes of low platelet counts and the complications that go with them. Other people may have long-term health problems from intracerebral hemorrhage or gastrointestinal bleeding.
ITP is not contagious and poses no risk to others.
If a person with ITP is hemorrhaging severely, the first treatment will be a transfusion of platelets. In some cases, the platelet count returns to normal on its own. This spontaneous remission of the disease is more common in children with ITP and rare in adults.
Corticosteroids, such as methylprednisolone or dexamethasone, are given to suppress the immune response. These can be given either intravenously or as tablets to be taken orally.
If steroid therapy does not improve the platelet count, more aggressive interventions can be tried. These include using intravenous immunoglobulin, also called IVIG. IVIG binds the autoantibodies that are attacking the platelets and removes them from the system. Once they are removed from the bloodstream, they cannot destroy the platelets. This treatment is very expensive and requires intravenous administration of medication.
To remove the autoantibodies causing the disorder, the person's blood can be filtered using a technique called plasmapheresis. A large catheter is placed into a blood vessel, and the blood is filtered through the plasmapheresis unit, removing the autoantibodies. This treatment is usually reserved for severe cases of ITP.
A splenectomy, or removal of the spleen, can be performed. Often this will cure the condition. Other experimental treatments have been tried with varying results.
Medications used to suppress the immune system may cause allergic reactions or increased risk of infection. Surgery can cause bleeding, infection, and allergic reaction to the anesthesia.
Treatment of ITP continues until a normal platelet count is restored. Then, the platelet count is monitored, and treatment can begin again if the platelet count begins to fall.
ITP is monitored by repeated complete blood counts, or CBCs. Any new or worsening symptoms should be reported to the healthcare provider.
Author:Bill Harrison, MD
Editor:Ballenberg, Sally, BS
Reviewer:Eileen McLaughlin, RN, BSN