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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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Dexamethasone for treatment of chronic ITP in children - immune thrombocytopenic purpura - Tips from Other Journals
From American Family Physician, 5/1/97 by Richard Sadovsky

Immune thrombocytopenic purpura (ITP) in children spontaneously remits in 80 percent of cases. For those who do not recover, the disease can cause severe limitations of normal daily activities. Most of these children do not have serious bleeding and do not need therapy. Some, however, have repeated nose bleeds, ecchymoses and hematomas. Many patients respond to splenectomy, but postsplenectomy sepsis is a serious complication. Physicians have attempted to maintain safe platelet levels with IgG administration or with low doses of steroids. Adult studies have demonstrated that repeat courses of high-dose dexamethasone therapy (i.e., 40 mg per day for four consecutive days every four weeks) can increase the number of platelets with minimal side effects. Borgna-Pignatti and associates evaluated the efficacy of pulse therapy with high-dose dexamethasone in children with chronic ITP.

Seventeen patients between the ages of four and 17 years with symptomatic ITP of six months' to 14 years' duration were enrolled in the study. All of the patients had platelet counts less than 20,000 per [mm.sup.3] (20 x [10.sup.9] per L). Patients received dexamethasone, 20 mg per [m.sup.2] orally in two divided doses for four days every four weeks, for six courses. Platelet counts and clinical condition were monitored for 12 months.

Platelet counts returned to normal in six (35 percent) of the children one month after the end of therapy. Five of these six patients still had normal platelet counts at the end of one year. Two patients with previous splenectomy were nonresponders. Side effects included fatigue or irritability, or both, anxiety, abdominal pain, striae, acne and weight gain. Children with shorter duration of disease before treatment responded better than those who had the disease for longer than 30 months. None of the patients who had the disease for more than 30 months responded to dexamethasone.

The authors conclude that pulsed high-dose dexamethasone therapy can help a small percentage of children with symptomatic chronic ITP. This treatment should probably be tried before splenectomy. However, a randomized, prospective trial designed to definitively confirm the effectiveness and safety of high-dose dexamethasone therapy is warranted before widespread recommendations can be made.

RICHARD SADOVSKY, M.D. Borgna-Pignatti C, et al. A trial of high-dose dexamethasone therapy for chronic idiopathic thrombocytopenic purpura in childhood. J Pediatr 1997;130:13-6.

COPYRIGHT 1997 American Academy of Family Physicians
COPYRIGHT 2004 Gale Group

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