Thrombocytopenia and immune thrombocytopenia

Overview & Definition

A healthy two-year-old who was entirely well last week is brought in covered in bruises and pinhead red spots, and the blood test shows a platelet count that has fallen to single digits. The child looks well, is running around the waiting room, and the rest of the blood count is normal. This is the classic face of childhood immune thrombocytopenia, and it is one of the commonest and most reassuring diagnoses in paediatric haematology once it is properly understood. Immune thrombocytopenia, always abbreviated ITP, is an autoimmune disorder in which the body makes antibodies against its own platelets, the antibody-coated platelets are destroyed in the spleen, and the platelet count falls until the bruising and the petechiae appear. [3][4]

The name itself carries a lesson, because it has changed. The condition was once called idiopathic thrombocytopenic purpura, meaning a purpura of unknown cause, and the fellow may still see the abbreviation ITP used that way in older texts. The international working group of Rodeghiero and colleagues, reporting in Blood in 2009, retired the word idiopathic and replaced it with immune, because the autoimmune mechanism is now firmly established, and the word purpura was dropped, because many children bruise without true purpura. The abbreviation ITP survives, but it now means immune thrombocytopenia. [4]

Three ideas make this topic central to the paediatric exam, and each is a deliberate decision rather than a reflex. The first is that the diagnosis is clinical and is made by exclusion, because ITP is defined as an isolated thrombocytopenia with a platelet count under 100 times ten to the nine per litre in a child who is otherwise well, with no other cytopenias and no blasts on the blood film. The second is the ASH 2019 observation-first principle, which holds that a child with no bleeding or only mild skin bleeding is managed by observation regardless of how low the count has fallen. The third is the distinction between the phases of the disease, because the child whose thrombocytopenia persists beyond twelve months moves into chronic ITP and into a different set of second-line drugs. [1][4]

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1. [1]Neunert C, Terrell DR, Arnold DM American Society of Hematology 2019 guidelines for immune thrombocytopenia. Blood Adv, 2019.PMID 31794604
2. [2]Provan D, Arnold DM, Bussel JB Updated international consensus report on the investigation and management of primary immune thrombocytopenia. Blood Adv, 2019.PMID 31770441
3. [3]Cooper N, Ghanima W Immune Thrombocytopenia. N Engl J Med, 2019.PMID 31483965
4. [4]Rodeghiero F, Stasi R, Gernsheimer T Standardization of terminology, definitions and outcome criteria in immune thrombocytopenic purpura of adults and children: report from an international working group. Blood, 2009.PMID 19005182
5. [5]Kühne T, Buchanan GR, Zimmerman S A prospective comparative study of 2540 infants and children with newly diagnosed idiopathic thrombocytopenic purpura (ITP) from the Intercontinental Childhood ITP Study Group. J Pediatr, 2003.PMID 14615730
6. [6]Imbach P, Kühne T, Müller D Childhood ITP: 12 months follow-up data from the prospective registry I of the Intercontinental Childhood ITP Study Group (ICIS). Pediatr Blood Cancer, 2006.PMID 16086422
7. [7]Kühne T, Berchtold W, Michaels LA Newly diagnosed immune thrombocytopenia in children and adults: a comparative prospective observational registry of the Intercontinental Cooperative Immune Thrombocytopenia Study Group. Haematologica, 2011.PMID 21880634
8. [8]Blanchette V, Imbach P, Andrew M Randomised trial of intravenous immunoglobulin G, intravenous anti-D, and oral prednisone in childhood acute immune thrombocytopenic purpura. Lancet, 1994.PMID 7915773
9. [9]Mithoowani S, Arnold DM First-Line Therapy for Immune Thrombocytopenia. Hamostaseologie, 2019.PMID 31170773
10. [10]Bussel JB, de Miguel PG, Despotovic JM Eltrombopag for the treatment of children with persistent and chronic immune thrombocytopenia (PETIT): a randomised, multicentre, placebo-controlled study. Lancet Haematol, 2015.PMID 26688484
11. [11]Neunert CE, Grace RF Thrombopoietin-receptor agonists in children with immune thrombocytopenia. Lancet, 2015.PMID 26231462
12. [12]Grace RF, Despotovic JM, Bennett CM Physician decision making in selection of second-line treatments in immune thrombocytopenia in children. Am J Hematol, 2018.PMID 29659042