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Idiopathic thrombocytopenic purpura (ITP), also called immune thrombocytopenic purpura, is a bleeding disorder in which your blood has difficulty clotting due to an unusually low number of platelets. Platelets (thrombocytes) are colorless blood cells that stop blood loss by clumping together at the site of a blood vessel injury and forming plugs in vessel holes.

People with idiopathic thrombocytopenic purpura, because of their low platelet count, tend to bruise easily and bleed longer when injured. Nosebleeds and bleeding gums also are common.

Idiopathic thrombocytopenic purpura is often divided into two categories: acute and chronic. Acute ITP is the most common form and occurs most frequently in children, typically after a viral infection. It usually goes away on its own within six months. Chronic ITP lasts longer than six months and is more common in adults.

Treatment of idiopathic thrombocytopenic purpura depends on your signs and symptoms and platelet count. If no bleeding problems are present and the platelet count isn't too low, treatment for idiopathic thrombocytopenic purpura usually isn't necessary. The goal of treatment for both children and adults is to create a safe platelet count and avoid bleeding complications. Treatment may include the use of medications and, in some cases, surgery.

Signs that typically indicate a low platelet count and possibly idiopathic thrombocytopenic purpura include:

• Easy or excessive bruising (purpura)
• Superficial bleeding into your skin that appears as a rash of pinpoint-sized reddish-purple spots (petechiae), usually on your lower legs
• Prolonged bleeding from cuts
• Spontaneous bleeding from your gums or nose
• Blood in urine or stools
• Unusually heavy menstrual flows
• Profuse bleeding during surgery

Serious or widespread bleeding indicates an emergency and requires immediate care.

The exact cause of idiopathic thrombocytopenic purpura is unknown. This is why it's referred to as idiopathic, which means "of unknown cause." However, scientists do know that with ITP, the immune system malfunctions and begins attacking platelets as if they were foreign substances.

Antibodies produced by your immune system attach themselves to the platelets, marking the platelets for destruction. The spleen, which helps your body fight infection, recognizes the antibodies and removes the platelets from your system. The result of this case of mistaken identity is a lower number of platelets than normal.

Normally, you have anywhere from 150,000 to 450,000 platelets per microliter of circulating blood. As the number of your platelets decreases, your risk of bleeding increases. The greatest risk is when platelet count falls very low — below 10,000 platelets per microliter. At this point, internal bleeding may occur despite a lack of any injury, although this is rare.

In children with acute ITP, the disorder often follows a viral illness, such as the mumps, a respiratory infection or a flu-like illness. It may be that such an infection sets off the immune system, triggering it to malfunction. But ITP in adults isn't linked to infections.

If you or your child has abnormal bleeding or bruising, or develops a rash of pinpoint-sized red spots (petechiae), see your doctor. Also, see your doctor if you're a woman and develop increased menstrual bleeding. A number of conditions can cause a low platelet count, including ITP. Because some of these conditions can be serious, it's important that your doctor evaluate your signs and symptoms promptly.

Doctors usually diagnose idiopathic thrombocytopenic purpura by excluding other possible causes of bleeding and a low platelet count, such as an underlying infection or illness or medications you may be taking. If no other underlying problem is causing your signs and symptoms, then a diagnosis of ITP may be made.

In addition to taking your medical history and performing a physical exam, your doctor may order the following tests when checking for ITP:

• Complete blood count. This common blood test is used to determine the number of white and red blood cells and platelets in a sample of your blood. With ITP, white and red blood cell counts are usually normal even though the platelet count is low. In adults with mild ITP who have no signs or symptoms, a low platelet count may be discovered coincidentally when this blood test is performed for a different purpose.
• Blood smear. A sample of your blood is placed on a slide and observed under a microscope. This test is often used to confirm the number of platelets observed in a complete blood count.

• Bone marrow examination. Another test that may help identify the cause of a low platelet count is a bone marrow examination. Platelets are produced in your bone marrow. An underlying problem, such as certain causes of anemia or leukemia, can affect your bone marrow's production of platelets and decrease your platelet count.

  A specialist, such as a doctor who specializes in blood disorders (hematologist) or in cancer (oncologist), usually performs this test. A needle is used to draw a sample of bone marrow cells for examination under a microscope.

  With ITP, however, your bone marrow is normal because the low platelet count is caused by immune-related destruction of platelets, not by impaired production of platelets.

The biggest risk associated with idiopathic thrombocytopenic purpura is bleeding, especially bleeding into the brain (intracranial hemorrhage), which can be fatal. Major bleeding is rare with ITP, however.

Complications may arise from the treatment therapies — corticosteroids and surgery — used for chronic or severe ITP. Long-term use of corticosteroids can cause serious side effects, including osteoporosis, cataracts, loss of muscle mass and increased risk of infection. Removal of your spleen (splenectomy), which may be performed if corticosteroids aren't working, also makes you permanently more vulnerable to infection, although the risk of an overwhelming infection in a healthy person who's had a splenectomy is small.

Pregnancy
Pregnant women with mild ITP usually have a normal pregnancy and delivery. However, antibodies to platelets can cross the placenta and affect the baby's platelet count. In some cases, a baby may be born with a low platelet count. If this happens, your baby's doctor will want to monitor the platelet count for several days. The baby's platelet count usually improves without treatment. If the count is very low, treatment can help speed recovery.

If you're pregnant and your platelet count is very low or you have bleeding, you're more at risk of heavy bleeding during delivery. Your doctor will discuss treatment with you, taking into account the effects on your baby. Treatment is aimed at maintaining a stable platelet count, especially during delivery.

Idiopathic thrombocytopenic purpura is usually treated by a doctor who specializes in blood disorders (hematologist). The goal of treating ITP is to ensure a safe platelet count and prevent bleeding complications while minimizing treatment side effects.

Because of the potential complications of both the disease and its treatment, it's important for you and your doctor to carefully weigh the benefits and risks of treatment. For example, some people find that the side effects of treatment are more burdensome than the effects of the disease itself. Treatment decisions are usually based on:

• Severity of signs and symptoms (active bleeding is usually an indication for treatment)
• Platelet count
• Age
• Risk of bleeding relative to lifestyle, such as participation in sports or other vigorous physical activities that may predispose you to injury
• Risk of bleeding based on other medical conditions (high blood pressure, infections, alcoholism, chronic liver disease, peptic ulcer) or medications
• Potential side effects of ITP therapies
• Your own preferences

In children, idiopathic thrombocytopenic purpura usually runs its course without the need for treatment. About 80 percent of children with idiopathic thrombocytopenic purpura recover completely within six months. Even in those children who develop chronic ITP, complete recovery may still occur, even years later.

Adults with mild cases of ITP may require nothing more than regular monitoring of signs, symptoms and platelet checks.

If your symptoms are troublesome and your platelet count is low given your lifestyle and risk of bleeding, you and your doctor may opt for treatment. Treatment usually consists of medications and, sometimes, surgery. Also, your doctor may have you discontinue certain drugs that can inhibit your already-reduced platelet function, such as aspirin, ibuprofen (Advil, Motrin, others) and the blood-thinning medication warfarin (Coumadin).

Medications
Common medications used to treat idiopathic thrombocytopenic purpura include:

• Corticosteroids. The first line of therapy for ITP is the use of corticosteroids, usually prednisone. Prednisone can help raise your platelet count by decreasing the activity of your immune system. Once your platelet count is back to a safe level, you can gradually discontinue taking the prednisone under the direction of your doctor. In general, this takes about four to six weeks.

  About 70 percent of adults experience a relapse after discontinuing the corticosteroids. A new course of corticosteroids may be pursued; however, long-term use of these medications has potentially serious side effects, including cataracts, high blood sugar, increased risk of infections, loss of calcium from bones, menstrual irregularities, suppressed adrenal gland hormone production, thin skin, obesity, weakness in shoulders and thighs, easy bruising and slower wound healing. You and your doctor will want to weigh the benefits of the medication against these risks. If you've taken corticosteroids for longer than three months, your doctor will likely recommend that you take calcium and vitamin D supplements to help maintain your bone density.

• Intravenous immunoglobulin (IVIG). If you need a rapid elevation in platelet count, such as in the case of critical bleeding or in preparation for surgery, you may receive medications such as immunoglobulin or anti-(Rh) D immunoglobulin through a needle placed in your vein (intravenously). These medications are quick and effective, but their benefits usually wear off in a couple of weeks.

Surgery
If you have moderate to severe ITP and the initial course of prednisone isn't helping, your doctor may recommend removal of your spleen (splenectomy). This eliminates the main focus of platelet destruction in your body and improves your platelet count. Improvement is usually seen in a couple of weeks.

One of the risks of splenectomy is an increased susceptibility to infection. But if you were in good health prior to your splenectomy, this risk is low. Before surgery, you'll likely receive preventive immunizations to reduce your risk of certain types of infection.

Splenectomy is rarely performed in children because of their high rate of spontaneous remission.

Emergency treatment
Although rare, severe bleeding can occur in anyone with ITP, regardless of age. Severe or widespread bleeding is life-threatening and demands emergency care. This usually includes transfusions of platelet concentrates, intravenous methylprednisolone (a type of corticosteroid) and intravenous immunoglobulin.

Other treatments
If neither the initial round of corticosteroids nor a splenectomy has helped you achieve remission and your symptoms are severe, your doctor may recommend another course of corticosteroids, usually at the lowest dose possible.

Other possible treatments may include the use of immunosuppressant drugs such as rituximab (Rituxan) — the safest and most commonly used of this group — cyclophosphamide (Cytoxan), azathioprine (Imuran) or vinca alkaloids (Vincasar, Velban), but side effects can be risky.

A number of people with ITP are also infected with Helicobacter pylori (H. pylori). Elimination of the infection has helped increase platelet count in some people. But the results for this type of therapy are inconsistent and need to be studied further.

If you have idiopathic thrombocytopenic purpura, the following steps may help control your risk of complications, such as bleeding and infection:

• Avoid platelet-impairing medications. Over-the-counter drugs such as aspirin and ibuprofen (Advil, Motrin, others) can impair platelet function.
• Limit alcohol. Excessive alcohol intake can impair blood clotting.
• Choose low-impact physical activities. Your doctor may recommend that you or your child avoid competitive sports or other activities that might increase the risk of injury and bleeding.
• Watch for signs of infection. If you've had your spleen removed, be alert to any signs of infection, including fever, and seek prompt treatment. Infection in someone who's had a splenectomy may be more severe and last longer than in someone who still has an intact spleen.