What is Immune Thrombocytopenia?

Definition of ITP

Immune thrombocytopenia (ITP), once called idiopathic thrombocytopenic purpura, is a condition where your body’s immune system attacks and destroys your platelets, causing low platelet counts (thrombocytopenia). Platelets are needed to clot blood, and if you do not have enough, you may experience bleeding.   

Symptoms of ITP

Many people with ITP are without symptoms. When they appear, symptoms of ITP are related to the increased risk of bleeding due to your low platelet count. Such symptoms include:    

• Nosebleeds
• Bleeding from the gums
• Blood in urine or stool
• Heavy menstrual bleeding (previously known as menorrhagia)
• Petechiae—these small red dots might resemble a rash, but are actually a small amount of bleeding under the skin
• Easy bruising—the bruises may be large and able to be felt beneath the skin
• Blood blisters in the inside of the mouth known as purpura

Causes of ITP 

In general, your platelet count drops in ITP because your body makes antibodies that attach to the platelets to mark them for destruction. When these platelets flow through the spleen (an organ in the abdomen that filters blood), it recognizes these antibodies and destroys the platelets. In addition, the production of platelets may be reduced. ITP typically develops after some inciting event, but sometimes your healthcare provider may be unable to determine what this event was. 

• Viruses: In children, ITP is often triggered by a viral infection. The viral infection usually occurs a couple of weeks prior to the development of ITP. While the immune system makes antibodies to fight the viral infection, it accidentally also makes antibodies that attach to the platelets.
• Immunizations: ITP has been associated with the administration of the MMR (measles, mumps, rubella) vaccine. It generally occurs within six weeks of receiving the vaccine. It is important to recognize that this is a very rare event, with 2.6 cases occurring for every 100,000 MMR vaccinations given. This risk is smaller than the risk of developing ITP if you had measles or rubella infection. Severe bleeding is rare in these cases, and, in more than 90% of people, ITP will resolve within 6 months.
• Autoimmune disease:  ITP is considered an autoimmune disorder and is associated with other autoimmune diseases like lupus and rheumatoid arthritis. ITP may be the initial presentation of one of these medical conditions.

Diagnosis of ITP

Similar to other blood disorders, like anemia and neutropenia, ITP is identified on a complete blood count (CBC). There is no single diagnostic test for ITP. It is a diagnosis of exclusion, meaning other causes have been ruled out. In general, only the platelet count is decreased in ITP; the white blood cell count and hemoglobin are normal. Your healthcare provider may have the platelets examined under a microscope (a test called a peripheral blood smear) to ensure that the platelets are decreased in number but appear normal. In the midst of the workup, you may have other testing to rule out cancer or other reasons for a low platelet count, but this is not always required. If your ITP is thought to be secondary to an autoimmune disease, you may have to test specifically for this. 

Treatment of ITP 

Currently, the treatment of ITP is dependent upon the presence of bleeding symptoms rather than a specific platelet count. The goal of therapy is to stop bleeding or to bring the platelet count up to a "safe" range. Although technically not a "treatment," people with ITP should avoid taking aspirin or ibuprofen-containing medications, as these medications decrease the function of platelets. 

• Observation: If you are not having any bleeding symptoms currently, your healthcare provider may choose to watch you closely without prescribing medications.
• Steroids: Steroids like methylprednisolone or prednisone are the most common medication used to treat ITP worldwide. Steroids reduce the destruction of platelets in the spleen. Steroids are very effective, but it may take more than a week to increase your platelet count.
• IVIG: Intravenous immune globulin (IVIG) is a common treatment for lTP. It is generally used for patients with bleeding who need a rapid rise in platelet count. It is administered as an intravenous (IV) infusion over several hours.
• WinRho: WinRho is a IV medication that can be used to increase the platelet count in people with certain blood types. It is a faster infusion than IVIG.
• Platelet transfusion: Platelet transfusions are not always helpful in people with ITP, but may be used in certain circumstances, such as if you need to undergo an operation. The other common situation when platelet transfusion may be considered is when a patient presents with a significant bleeding event and there is a need to try to stop bleeding immediately.

If your ITP persists and does not respond to initial treatments, your healthcare provider may recommend other treatments, such as the following. 

• Splenectomy:  In ITP, the platelets are destroyed in the spleen. By removing the spleen, the life expectancy of the platelets can be increased. Benefits and risks should be weighed prior to deciding to remove the spleen.
• Rituximab:  Rituximab is a medication called a monoclonal antibody. This medication helps to destroy the white blood cells, called B-cells, that produce the antibodies against platelets. The hope is that when your body produces new B-cells, they will no longer make these antibodies.
• Thrombopoietin agonists: Some of the newest treatments are thrombopoietin (TPO) agonists. These medications are eltrombopag (oral) or romiplostim (subcutaneous); they stimulate your bone marrow to make more platelets.

ITP Differences in Children and Adults 

It is important to note that the natural history of ITP is often different in children versus adults. Approximately 80% of children diagnosed with ITP will have a complete resolution. Adolescents and adults are more likely to develop chronic ITP, which becomes a lifelong medical condition that may or may not require treatment.