Idiopathic thrombocytopenic purpura (ITP)

Definition

Idiopathic thrombocytopenic purpura is a bleeding disorder in which the immune system destroys platelets, which are necessary for normal blood clotting. Persons with the disease have too few platelets in the blood.

ITP is sometimes called immune thrombocytopenic purpura.

Alternative Names

Immune thrombocytopenic purpura; ITP

Causes, incidence, and risk factors

ITP occurs when certain immune system cells produce antibodies against platelets. Platelets help your blood clot by clumping together to plug small holes in damaged blood vessels.

The antibodies attach to the platelets. The spleen destroys the platelets that carry the antibodies.

In children, the disease sometimes follows a viral infection. In adults, it is more often a chronic (long-term) disease and can occur after a viral infection, use of certain drugs, pregnancy, or an immune disorder.

ITP affects women more frequently than men, and is more common in children than adults. The disease affects boys and girls equally.

Symptoms

• Abnormally heavy menstruation
• Bleeding into the skin causes a characteristic skin rash called pinpoint red spots or petechial rash
• Easy bruising
• Nosebleed or bleeding in the mouth

Signs and tests

Laboratory tests will be done to see how well your blood clots and to check your platelet count.

• A complete blood count (CBC) shows a low number of platelets.
• Blood clotting tests (PTT and PT) are normal.
• Platelet associated antibodies may be detected.

A bone marrow aspiration or biopsy appears normal.

Treatment

In children, the disease usually goes away without treatment. Some children, however, may need treatment.

Adults are usually started on an anti-inflammatory medicine called prednisone. In some cases, surgery to remove the spleen (splenectomy) is recommended. This can help increase the platelet count in about 50% of patients. However, other drug treatments are usually recommended instead.

If the disease does not get better with prednisone, other treatments may include:

• A medicine called danazol (Danocrine) taken by mouth
• Injections of high-dose gamma globulin (an immune factor)
• Drugs that suppress the immune system
• Filtering antibodies out of the blood stream
• Anti-RhD therapy for people with certain blood types

People with ITP should not take aspirin, ibuprofen, and warfarin because these drugs interfere with platelet function and blood clotting, and bleeding may occur.

Expectations (prognosis)

With treatment, the chance of remission (a symptom-free period) is good. Rarely, ITP may become a long-term condition in adults and reappear, even after a symptom-free period.

Complications

Sudden and severe loss of blood from the digestive tract may occur. Bleeding into the brain may also occur.

Calling your health care provider

Go to the emergency room or call the local emergency number (such as 911) if severe bleeding occurs, or if other new symptoms develop.

Prevention

The causes and risk factors are unknown, except in children when it may be related to a viral infection. Prevention methods are unknown.

References

McMillan R. Hemorrhagic disorders: abnormalities of platelet and vascular function. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 179.