ITP Background Information

Intercontinental Cooperative ITP Study group

Immune Thrombocytopenic Purpura (ITP)

Primary immune thrombocytopenic purpura (also known as idiopathic thrombocytopenic purpura) is a bleeding disorder characterized by increased destruction of circulating platelets resulting in thrombocytopenia (platelet count <150x109/L) with normal or enhanced bone marrow megakaryocytes. Immunologic mechanisms play an important role in the pathophysiology of ITP. The condition is traditionallly divided into acute and chronic forms based on the duration of thrombocytopenia. Acute ITP is a relatively common disorder of young children that typically occurs a few days to a few weeks after an infectious illness, often a viral upper respiratory tract infection. It is generally a benign and self-limiting disorder with an excellent prognosis.

Primary chronic ITP is defined as a thrombocytopenia persisting for more than 6 months and arises in otherwise healthy children. Secondary causes of autoimmune thrombocytopenia include systemic lupus erythematosus, viral infections, and lymphoproliferative disorders. There are no specific predictors of chronic ITP, although older age in children and an insidious onset of presentation seem to be associated with chronic ITP. This form of ITP accounts for 10-20% of all childhood patients, and almost all adults with ITP.

Treatment

Management of children with acute ITP is controversial. The benign natural history of the disorder has to be taken into account as well as the small but definite risk of a severe bleeding such as intracranial hemorrhage which seems to be restricted to a platelet count of <20x109/L. The incidence of intracranial hemorrhage continues to be controversial and is approximately 1% in children with acute ITP, however, large studies investigating this matter are missing. Traditional treatment options comprise of intravenous immunoglobulins (IVIG), steroids, anti-Rh(D), and no therapy

Treat the bleeding rather than platelet counts!

The goal of treatment of chronic ITP in childhood is to reduce morbidity and mortality, rather than to produce clinically insignificant changes of platelet values. Corticosteroids and IVIG are used to increase platelet to safe hemostatic levels, however, recurrence of thrombocytopenia is common and repeated treatment courses are required. Long-term corticosteroid treatment may lead to unacceptable adverse effects (e.g. Cushing syndrome, growth retardation, diabetes mellitus, or hypertension) and long-term IVIG results in high costs. Splenectomy may be an effective treatment option, however there are several reasons to delay surgery. About one-fifth of children with chronic ITP fail to respond to splenectomy. Overwhelming postsplenectomy infection due to encapsulated organisms limits its safety, mainly in patients younger than 5 years of age. Perhaps most important, the potential for spontaneous remission justifies delaying splenectomy. The immunomodulatory effect of IVIG and corticosteroids given as short courses at regular intervals is currently under investigation.

 


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