Immune Thrombocytopenic Purpura in Children

Dr. Priti S. Mehta
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Abstract
Immune thrombocytopenia (ITP) is commonly encountered by general physicians and paediatricians in their day to day practice. With rapid advances in the field of hematology, not only the insight as to the pathophysiology has changed but the terminologies too have changed. Approval of the use of Thrombopoeitin mimetics in children has added a ray of hope for children suffering from chronic ITP.

The International Working Group (IWG) consensus panel has defined primary ITP as a platelet count less than 100 × 109 /L in the absence of other causes or disorders that may be associated with thrombocytopenia.
IWG also defines ITP as newly diagnosed (diagnosis to 3 months), persistent (3 to 12 months from diagnosis), or chronic (lasting for more than 12 months). These definitions have not been formally validated and may not apply to patients with secondary forms of ITP.6

The terminology of ITP is now known as Immune Thrombocytopenic Purpura unlike Idiopathic Thrombocytopenic Purpura in the past and indicates an underlying autoimmune disease in Children.1 The common age of presentation in children is between 1-7 years of age with an incidence of approximately 5 per 100,000 children and 2 per 100,000 adults.2
Children have varied manifestations like petechiae, ecchymosis, mucosal bleeds but the percentage of children presenting with life threatening bleeds is negligible (0.2-0.9%).3 This is because the platelets in circulation are relatively young platelets adequate in function unlike in aplastic anemia. The latest concept is that in addition to an increased peripheral platelet destruction there is also a decreased platelet production.ITP may occur either as an isolated phenomenon (primary) or secondary to other disorders (secondary) such as antiphospholipid syndrome, SLE, autoimmune thrombocytopenia (e.g. Evan’s syndrome - which is associated with autoimmune thrombocytopenia with coincident hemolytic anemia), common variable immune deficiency, drug administration, Infection with cytomegalovirus, Helicobacter pylori, hepatitis C, human immunodeficiency virus, varicella zoster, lymphoproliferative disorders, bone marrow transplantation, post vaccination.

The pathophysiology is postulated to be twofold:
1) Immune mediated destruction of platelets.
ITP is an autoimmune disorder in which immunologic destruction of otherwise normal platelets occurs in response to an unknown stimulus. Antiplatelet antibodies opsonize the platelets and with the help of Fc ? receptors are attached to antigen-presenting cells. Macrophages then phagocytose these opsonised platelets. Some cryptic epitopes from platelet antigens stimulate platelet-specific T cells which in turn stimulate B cells to produce more antiplatelet antibodies.4
2) Decreased production of platelets
A rise in platelet count after administering TPO mimetics confirms the role of thrombopoietin (TPO) in reduced thrombopoiesis in ITP and stimulation with TPO mimetics.5


References
Immune Thrombocytopenic Purpura in Children Immune Thrombocytopenic Purpura in Children 6/28/2016
Immune Thrombocytopenic Purpura In Children - Presentation >>
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