Immune Thrombocytopenia (ITP) in Emergency Medicine: Practice Essentials, Pathophysiology, Etiology (original) (raw)

Practice Essentials

Immune thrombocytopenia (ITP), previously known as idiopathic thrombocytopenic purpura, is defined as isolated thrombocytopenia with normal bone marrow and in the absence of other causes of thrombocytopenia. ITP has two distinct clinical syndromes, manifesting as an acute condition in children and a chronic condition in adults. [1]

Isolated thrombocytopenia on a complete blood cell count (CBC) is the key laboratory finding (see Workup). Treatment depends on patient characteristics and clinical circumstances and ranges from observation only to pharmacologic therapy to splenectomy (see Treatment and Medication).

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Pathophysiology

ITP is primarily a disease of increased peripheral platelet destruction, with most patients having antibodies to specific platelet membrane glycoproteins. Relative marrow failure may contribute to this condition, since studies show that most patients have either normal or diminished platelet production.

Acute ITP often follows an acute infection and has a spontaneous resolution within 2 months. Chronic ITP persists longer than 6 months without a specific cause.

Malik et al have identified cytotoxic CD8+ T cells as an antibody-independent mechanism of platelet destruction in chronic ITP. These researchers demonstrated that adults with chronic ITP have clonal expansion of terminally differentiated effector memory CD8+ T cells (TEMRA), compared with age-matched controls. TEMRAs form aggregates with autologous platelets, release interferon gamma, and trigger platelet activation and apoptosis via the T-cell receptor–mediated release of cytotoxic granules. [2]

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Etiology

ITP develops when platelets become coated with immunoglobulin G (IgG) autoantibodies to platelet membrane antigens, resulting in splenic sequestration and phagocytosis by mononuclear macrophages. The resulting shortened life span of platelets in the circulation, together with incomplete compensation by increased platelet production by bone marrow megakaryocytes, results in a decreased number of circulating platelets.

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Epidemiology

Frequency

United States

Incidence rates are as follows:

International

According to studies in Denmark and England, childhood ITP occurs in approximately 10-40 cases per 1,000,000 per year. [3] A prospective, population-based study in Norway indicated an incidence of 53 per 1,000,000 in children younger than 15 years. [4] A study in Kuwait reported a higher incidence of 125 cases per 1,000,000 per year.

Mortality/morbidity

Hemorrhage represents the most serious complication; intracranial hemorrhage is the most significant. The mortality rate from hemorrhage is approximately 1% in children and 5% in adults. In patients with severe thrombocytopenia, predicted 5-year mortality rates from bleeding are significantly raised in patients older than 60 years versus patients younger than 40 years, 47.8% versus 2.2%, respectively. Older age and previous history of hemorrhage increase the risk of severe bleeding in adult ITP.

Spontaneous remission occurs in more than 80% of cases in children. However, it is uncommon in adults.

Sex- and age-related demographics

In acute ITP (children), distribution is essentially equal between males (52%) and females (48%). In chronic ITP (adults), the female-to-male ratio is 2.6:1. More than 72% of patients older than 10 years are female.

In children, peak incidence is at ages 2-4 years. Approximately 40% of all patients are younger than 10 years. In adults, peak incidence is at ages 20-50 years.

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Prognosis

Approximately 83% of children have a spontaneous remission, and 89% of children eventually recover. More than 50% recover within 4-8 weeks. Approximately 2% die.

Only 2% of adults have a spontaneous recovery; however, approximately 64% of adults eventually recover. Approximately 30% have chronic disease, and 5% die from hemorrhage.

Complications of immune thrombocytopenia and its treatment may include the following:

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Patient Education

Instruct patients to return for follow-up in order to assess for a potentially reduced platelet count. Emphasize close outpatient follow-up care. Because of the increased risk of bleeding, instruct patients to avoid aspirin products.

For patient education information, see Thrombocytopenia (Low Platelet Count).

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Author

Michael A Silverman, MD, FACEP Chairman, Department of Emergency Medicine, Virginia Hospital Center; Instructor of Emergency Medicine, Johns Hopkins University School of Medicine; Chief of Emergency Medicine, Harbor Hospital; Attending Emergency Physician, Harbor Hospital, St Agnes Healthcare, and Johns Hopkins Bayview Medical Center

Michael A Silverman, MD, FACEP is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, American Medical Association, Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Chief Editor

Gil Z Shlamovitz, MD, FACEP Professor of Clinical Emergency Medicine, Keck School of Medicine of the University of Southern California; Chief Medical Information Officer, Keck Medicine of USC

Gil Z Shlamovitz, MD, FACEP is a member of the following medical societies: American College of Emergency Physicians

Disclosure: Nothing to disclose.

Additional Contributors