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Idiopathic thrombocytopenic purpura

Idiopathic thrombocytopenic purpura is the condition of having a low platelet count (thrombocytopenia) of no known cause (idiopathic). As most causes appear to be related to antibodies against platelets, it is also known as immune thrombocytopenic purpura. Although most cases are asymptomatic, very low platelet counts can lead to a bleeding diathesis and purpura. more...

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Signs and symptoms

ITP occurs most often in women over 40 years of age. It may be acute, lasting for 6 months or less, or chronic, lasting for over a year. The acute type is more often seen in children and will cure itself in more than 80% of cases. The chronic type is more commonly seen in adults and it tends to get worse as the disease progresses.

Occasionally, ITP patients suffer from bruising, nosebleeds, and bleeding gums; this is the characteristic pattern of bleeding in platelet disorders. Bleeding normally does not occur unless the platelet count is very low (below about 10,000 per mm3, compared to a normal range of 150,000–400,000 per mm3).

Subarachnoid and intracerebral hemorrhage are very serious possible complications of this disease. Fortunately, these are rare in patients who are being treated.


In many cases, the cause is not actually idiopathic but autoimmune, with antibodies against platelets being detected in approximately 80% of patients. Most often these antibodies are against platelet membrane glycoproteins IIb-IIIa or Ib-IX, and are of the IgG type. The coating of platelets with IgG renders them susceptible to opsonization and phagocytosis by splenic macrophages.

The IgG autoantibodies are also thought to damage megakaryocytes, the precursor cells to platelets, but this is thought to contribute only slightly to the decrease in platelet numbers.


When measuring the platelet count, one has to bear in mind that the "normal values" for laboratory measures are all statistical. They are defined by the upper and lower 2.5th percentile. It is therefore possible to be completely healthy but to have a decreased platelet count. There is, however, a higher chance of pathology.

The diagnosis of ITP is a clinical one and is a diagnosis of exclusion. Low platelet count can be a feature of a large number of diseases and, when serious, warrants investigation by a hematologist. Secondary causes include leukemia, medications (e.g. quinine), lupus erythematosus and some other autoimmune disorders, cirrhosis (leading to thrombocytopenia from hypersplenism), HIV, congenital causes, and antiphospholipid syndrome. A bone marrow examination may be performed on patients over the age of 60 and people who do not respond to treatment, or when the diagnosis is in doubt.

Despite the destruction of platelets by splenic macrophages, the spleen is normally not enlarged. In fact, an enlarged spleen should lead a clinician to investigate other possible causes for the thrombocytopenia.

Accelerated formation of platelets results in the presence of abnormally large platelets which are seen in a peripheral blood smear. Overall bleeding time is prolonged in these patients, but prothrombin time (PT) and partial thromboplastin time (PTT) are normal (because the problem is with the platelets, not with the coagulation cascade).


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...About idiopathic thrombocytopenic purpura
From Nursing, 11/1/04 by Munson, Becky Lien

MYTH: Idiopathic thrombocytopenic purpura (ITP) is caused by abnormalities in the bone marrow.

FACT: An autoimmune bleeding disorder, ITP develops when antibodies destroy platelets in the periphery of the body, rather than in the liver or spleen, as normal. The resulting low platelet count causes bruising, petechiae, and abnormal bleeding. Severity of illness depends on the location, duration, and amount of bleeding.

MYTH: Because ITP is hereditary, genetic counseling is recommended.

FACT: Neither of the two types of ITP-acute in children and chronic in adults-has a genetic link.

MYTH: Acute ITP in children is often fatal.

FACT: About 50 children per million develop acute ITP annually; 83% recover spontaneously without treatment within 2 months. Only about 2% die. Onset of acute ITP often follows a viral illness or live virus vaccination.

MYTH: Bone marrow aspiration is standard to confirm a suspected ITP diagnosis.

FACT: Bone marrow aspiration is appropriate in children if thrombocytopenia persists despite treatment, but it's not a routine diagnostic procedure for ITP. The diagnosis of ITP is primarily based on the patient's history, physical exam, complete blood cell count, and examination of a peripheral blood smear. These results should rule out other possible causes of thrombocytopenia.

MYTH: Splenectomy is the first choice of treatment for ITP.

FACT: Splenectomy isn't indicated for patients with mild symptoms. However, Splenectomy may be appropriate if bleeding is severe or persistent and the patient's platelet count remains below 30,000/mm^sup 3^ after 6 weeks of medical therapy.

Most patients with platelet counts below 50,000/mm^sup 3^ are prescribed glucocorticoids, such as prednisone and methylprednisolone, and I.V. immune globulin to reduce inflammation and increase platelet count. Patients with platelet counts above 50,000/mm^sup 3^ and those with counts above 30,000/mm^sup 3^ who are asymptomatic or have only minor purpura may not need treatment.


Becky Lien Munson is nursing supervisor at the Washington School for the Deaf in Vancouver, Wash. Selected references for this article are available on request.

Copyright Springhouse Corporation Nov 2004
Provided by ProQuest Information and Learning Company. All rights Reserved

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