Immune Thrombocytopenia (ITP)


Immune thrombocytopenia (ITP) is an autoimmune disorder characterized by an abnormally low number of platelets (<100,000/µL) in the blood. The low platelet count is attributed to a dysfunctional immune system that targets both platelets and their precursors. The decreased platelet number manifests as a bleeding disorder with symptoms such as easy bruising, bleeding gums, and internal bleeding.1,2 ITP can be classified into the forms of acute and chronic and also into the types of primary and secondary.

Acute ITP

Acute (short-term) ITP is the most common type, occurring mainly in children 2 to 6 years old. In this temporary form of ITP, the symptoms start suddenly and last for 6 months or even less. Acute ITP often develops following a viral infection, such as chickenpox. The symptoms usually disappear within a few weeks without treatment. The chance of recurrence in acute cases is usually low.3,4

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Chronic ITP

In chronic (long-term) ITP, symptoms persist longer than 6 months and may occur for several years or even a lifetime. Chronic ITP may onset at any age. However, chronic ITP develops more frequently in adults than in children and is 2 to 3 times more common in females than in males. The chance of recurrence is high, so patients require continuous follow-up care by a hematologist. Treatment depends on the severity of bleeding and the platelet count. In people with chronic ITP, splenectomy is considered to decrease the rate of platelet destruction as the spleen is the most common site of antibody mediated platelet destruction.3,4

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Primary ITP

According to the international guidelines, ITP can also be classified as primary or secondary.5 Most adults with ITP have a primary form, which is an acquired autoimmune disorder that occurs in the absence of an identifiable cause. Thrombocytopenia is isolated and not associated with any other condition or disorder. In primary ITP, the low platelet count is the result of accelerated platelet destruction and inhibited platelet production in the bone marrow. Platelet destruction occurs when auto-antibodies against platelet membrane proteins (specifically, glycoprotein [GP] IIb/IIIa complex, GP Ib/IIa, and GP VI) coat the platelets, which are then cleared by tissue macrophages. In addition, platelet production is inhibited when the auto-antibodies impair megakaryopoiesis in the bone marrow.5-8

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Secondary ITP

Unlike primary ITP, secondary ITP is associated with underlying disorders such as autoimmune diseases (eg, systemic lupus erythematosus, rheumatoid arthritis, Evans syndrome, Sjögren syndrome, antiphospholipid syndrome); lymphoproliferative diseases (especially chronic lymphocytic leukemia); underlying immune dysregulation syndromes (eg, common variable immunodeficiency); chronic infections due to bacteria (eg, Helicobacter pylori) or viruses (eg, human immunodeficiency virus [HIV]), hepatitis C virus [HCV], Epstein-Barr virus [EBV], cytomegalovirus [CMV]), and drugs. Spontaneous remission occurs in approximately 80% of secondary ITP patients. Patients with secondary ITP may also present with hepatosplenomegaly, mucocutaneous bleeding in form of ecchymosis, petechiae, or purpura on the skin, gingival bleeding, vaginal, genitourinary system, or GI tract bleeding. However, retinal and conjunctival hemorrhages are rarely seen in secondary ITP.5-8 

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References

  1. Immune thrombocytopenia. NORD (National Organization for Rare Disorders). Accessed October 26, 2022.
  2. Platelet disorders – immune thrombocytopenia (ITP). NIH National Heart, Lung, and Blood Institute. Accessed October 26, 2022.
  3. Idiopathic thrombocytopenic purpura. Johns Hopkins Medicine. Accessed October 26, 2022.
  4. Types of immune thrombocytopenic purpura (ITP). Stanford Medicine Health Care. Accessed October 26, 2022.
  5. Tărniceriu CC, Hurjui LL, Florea ID, et al. Immune thrombocytopenic purpura as a hemorrhagic versus thrombotic disease: an updated insight into pathophysiological mechanisms. Medicina (Kaunas). 2022;58(2):211. doi:10.3390/medicina58020211
  6. Pietras NM, Pearson-Shaver AL. Immune thrombocytopenic purpura. StatPearls [Internet]. Updated May 10, 2022. 
  7. Zufferey A, Kapur R, Semple JW. Pathogenesis and therapeutic mechanisms in  immune thrombocytopenia (ITP). J Clin Med. 2017;6(2):16. doi:10.3390/jcm6020016
  8. Zlamal J, Bakchoul T. Acquired immune thrombocytopenia: an update on pathophysiology, diagnosis and management. Ann Blood. 2018;3:45. https://doi.org/10.21037/AOB.2018.10.02

Reviewed by Debjyoti Talukdar, MD, on 10/30/2022.

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