The body has enough work to do defending itself from the outside world, repairing injuries, and fighting off infections. So it seems unfair that there are also enemies within that body that are ready to attack. Such is the case with immune thrombocytopenic purpura (idiopathic thrombocytopenic purpura or ITP), where the body attacks and destroys platelets in the bloodstream, leading to an increased risk of bleeding.
Red and white blood cells are the star players in blood.
- Red blood cells are the carriers of hemoglobin so that the body can receive oxygen from the lungs and deliver it to the organs of the body in order for them to function.
- White blood cells are the armies of the body, fighting off infection.
- Platelets get no press and little respect (unless they are involved with a heart attack!). Their purpose is to begin the clotting process in the body. When a blood vessel is damaged, platelets are the first to arrive at the scene to plug the hole. Other blood proteins start to congregate to form fibrin that strengthens the platelet plug and ultimately forms a clot. Without enough platelets, the bleeding repair process fails and blood can leak out where it doesn't belong.
In ITP, the body's immune system doesn't recognize the surface of the platelet cell as part of the body. It coats the surface of the platelet cell with antibodies and the now-damaged platelet is removed from the bloodstream by the spleen, the organ whose job it is to clean and filter the blood of abnormal or damaged cells and other particles. If the platelet count drops too low, spontaneous bleeding can occur. The name, ITP, perfectly describes the situation. The immune system removes platelets and thrombocytopenia (thrombocyte=platelet + penia=low count, low platelet count) appears, causing purpura, a characteristic type of bruising or bleeding of the skin.
Other symptoms of ITP include:
The reason why ITP occurs is not quite certain.
In children, ITP often follows a viral infection and fortunately can resolve after a few months and may not need treatment. In adults, the reasons are less obvious and ITP may last a lifetime. It is important to make sure that the low platelet count is not due to liver disease or other blood disorders like leukemia. For that reason, ITP is a diagnosis of exclusion, meaning many tests may be done just to prove that they are normal.
Treatment protocols are designed to keep enough functioning platelets in the blood so that minor injuries don't cause major disasters. Bleeding into the brain is the most common cause of death from ITP, and it may be spontaneous or due to a minor injury. While most people have hundreds of thousands of platelets in a milliliter of blood, the treatment goal for patients with ITP is to keep the platelet count greater than 50,000 even though patients won't get a platelet transfusion unless the numbers drop well below that. Treatment options may range from observation to medications (for example, prednisone or danazol), platelet transfusion, or surgery to remove the spleen. Usually, the primary health care practitioner will seek input from a hematologist to tailor the treatment plan to the individual patient.
Not so long ago, ITP stood for idiopathic, not immune, purpura, meaning the cause was uncertain or unknown. The name change name signaled that progress was being made in understanding the reason why the body thinks that its own platelets don't belong. As research continues, new information may allow another name change, and that might lead to more satisfying treatment options that will replace disease control with disease cure.
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eMedicine.com. Immune Thrombocytopenic Purpura.
Stasi,R, etal. Idiopathic Thrombocytopenic Purpura: Current Concepts in Pathophysiology and Management. Thrombosis and Haemostasis. 2008:99(1). pp 4-13