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Chapter 68: Immune Thrombocytopenia

Kiarash Kojouri; Arafat Tfayli; James N. George

Updated chapter to come.

INTRODUCTION

Idiopathic Thrombocytopenic Purpura (ITP)

ITP is defined as isolated thrombocytopenia with no other clinically apparent associated conditions or causes of thrombocytopenia caused by accelerated destruction as well as impaired production of platelets by antiplatelet autoantibodies

 

Ballem PJ et al. J Clin Invest 1987;80:33–40

[British Committee for Standards in Haematology General Haematology Task Force] Br J Haematol 2003;120:574–596

George JN et al. Blood 1996;88:3–40

McMillan R. Semin Hematol 2007;44(4 Suppl 5):S3–S11

Epidemiology

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Epidemiology
Incidence: 1.6–3.2/105 per year, based on platelet count <50,000/mm3. Incidence increases among elderly, reaching 4.6/105 per year in persons >60 years old
Prevalence: 10/105
Median age: 56 years
Female-to-male ratio: 1.2–1.7/1; however, males and females are equally affected in the elderly
Mortality rate: Most adults with ITP have no excess mortality when compared with that of the general population. However, those with persistent thrombocytopenia (platelet count <30,000/mm3) at 2 years after initial presentation had higher mortality as compared to the general population (relative risk 4.2 [95% CI, 1.7–10.0]). The majority of deaths are a result of unrelated causes or complications of treatment, rather than hemorrhage

 

Frederiksen H, Schmidt K. Blood 1999;94:909–913

Neylon AJ et al. Br J Haematol 2003;122:966–974

Portielje JEA et al. Blood 2001;97:2549–2554

Segal JB, Powe NR. J Thromb Haemost 2006;4:2377–2383

Differential Diagnosis

  1. Pseudothrombocytopenia (platelet clumping in the presence of EDTA by naturally occurring autoantibodies to normally concealed epitopes on glycoprotein IIb/IIIa)

  2. Drug-induced thrombocytopenia (including nonprescription drugs and herbs)

  3. Secondary autoimmune thrombocytopenia, for example, CLL, SLE, antiphospholipid antibody syndrome (isolated presence of antinuclear antibodies in a patient with immune thrombocytopenia, without other clinical features of SLE, does not imply a diagnosis of SLE, although some of these patients will eventually develop full-blown SLE)

  4. Infectious disorders (HIV, HCV, EBV)

  5. Bone marrow failure (myelodysplasia)

  6. Congenital/hereditary nonimmune thrombocytopenia

  7. Hypersplenism caused by occult liver disease

  8. Incidental thrombocytopenia of pregnancy (also termed gestational thrombocytopenia)

  9. Thrombotic thrombocytopenic purpura/hemolytic uremic syndrome

  10. Chronic disseminated intravascular coagulation

 

[British Committee for Standards in Haematology General Haematology Task Force] Br J Haematol 2003;120:574–596

George JN et al. Ann Intern Med 1998;129:886–890

George JN et al. Blood 1996;88:3–40

Work-up

Objectives are to assess the type, severity, and duration of bleeding, and to exclude other etiologies

  1. CBC: Pseudothrombocytopenia from EDTA-dependent platelet agglutination (occurs in ≈ 0.1% of adults) or platelet adherence to neutrophils and monocytes (platelet rosetting) should be ruled out by examination of peripheral smear

  2. Peripheral blood smear: Findings consistent with the diagnosis of ITP include thrombocytopenia with normal-sized or slightly larger than normal platelets, and normal red and white blood cell morphology

  3. Bone marrow examination: The American Society of Hematology guidelines recommend bone marrow examination as appropriate to establish diagnosis in patients over age 60 years (because of the higher incidence of myelodysplasia), in those with atypical features in peripheral blood ...

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