Immune Thrombocytopenia (ITP)


Immune thrombocytopenia (ITP), previously called idiopathic thrombocytopenic purpura, is a bleeding disorder in which the number of platelets in the blood are markedly decreased, usually to values below 100,000/µL. In ITP, white blood cell count and hemoglobin levels are normal, and patients often present with a generalized purpuric rash.1,2 

Blood cells called platelets aid in the cessation of bleeding. Easy bruising, bleeding gums, and internal bleeding are all symptoms of platelet depletion. An immune response directed against one’s own platelets results in ITP. Purpura refers to the purple discoloration of the skin, as with a bruise.2 

Immune thrombocytopenia has two forms: acute and chronic. Acute ITP is the most common disease form, which is frequently noted in young children aged 2 to 6 years. Signs and symptoms may follow after a viral infection like chickenpox. The symptoms of acute ITP typically arise very suddenly and go away in less than 6 months, usually within a few weeks. The disease generally does not relapse. Chronic ITP can occur at any age, and symptoms can continue anywhere from 6 months to several years. Although it also affects adolescents, this form is more common in adults. Chronic ITP is 2 to 3 times more likely to affect female individuals than male individuals. Because chronic ITP can recur frequently, ongoing follow-up care with a hematologist is necessary.3 

Differential diagnoses include thrombotic thrombocytopenic purpura (TTP), hemolytic uremic syndrome (HUS), disseminated intravascular coagulation (DIC), myelodysplastic syndrome, lymphoproliferative disorders, infections such as human immunodeficiency virus (HIV) and hepatitis C, and drug-induced thrombocytopenia due to heparin, alcohol, and sulfonamides.4 

Thrombotic Thrombocytopenic Purpura

Both ITP and TTP affect platelets. Although they may present the same clinical manifestations, the illnesses have distinct causes, complications, and therapies.5 

Symptoms of ITP occur when platelets in the blood are insufficient to allow quick clotting, which results in the leakage of blood from small vessels. Symptoms of TTP arise as a result of abnormal blood vessel clot formation in organs, which impairs their ability to function. Other parts of the body may bleed because platelets are consumed by the improperly produced clots.5 

Read more about ITP signs and symptoms

TTP is an uncommon disease showing thrombotic microangiopathy that occurs due to an acquired autoantibody, resulting in a reduction in the activity of the von Willebrand factor-cleaving protease ADAMTS13. The disease causes hemolytic anemia and severe thrombocytopenia. While corticosteroids and rituximab may be used in the treatment of both ITP and TTP, immediate therapeutic plasma exchange, which is ineffective for ITP, represents an important therapy for TTP.6 

Hemolytic Uremic Syndrome

Thrombocytopenia, microangiopathic hemolytic anemia, and acute kidney injury are the hallmarks of this acute, fulminant illness. It is typically seen in children after an infection with Shiga toxin-producing bacteria (eg, Escherichia coli O157:H7), but it can also be seen in adults. HUS diagnosis relies on characteristic laboratory test abnormalities, such as hemolytic anemia with a negative direct antiglobulin test. Supportive therapy is the preferred course of treatment; eculizumab or ravulizumab are infrequently necessary.7 By contrast, ITP is usually autoimmune-related or secondary to systemic lupus erythematosus, HIV, or drugs (eg, quinine), but it can be idiopathic as well.8 

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Disseminated Intravascular Coagulation

This acquired disorder is characterized by intravascular activation of coagulation without a defined site of origin. This excessive thrombin state manifests clinically as thrombosis, embolism, and microvascular occlusion by fibrin thrombi, resulting in multiorgan dysfunction syndrome from tissue ischemia and hemorrhagic disease from platelet loss, the consumption of coagulation factors, and/or the accelerated formation of plasmin. A patient may have thrombosis and hemorrhage simultaneously.9 Thrombocytopenia is noted in both DIC and ITP. ITP, however, differs from DIC in terms of its pathophysiologic process, and it does not involve microangiopathic hemolytic anemia or coagulation activation.10

Read more about ITP pathophysiology

Other Common Differentials

Other common ITP differential diagnoses and possible causes of thrombocytopenia as indicated by patient history include: diseases that may be associated with ITP, such as hepatitis B, hepatitis C, and HIV infection; malignancies, such as lymphoproliferative diseases; and autoimmune or immunodeficiency diseases, including common variable immunodeficiency, systemic lupus erythematosus, and antiphospholipid syndrome. 

Additional ITP differential diagnoses include liver disease, alcohol abuse, exposure to environmental toxins, and responses to drugs, including chemotherapy medications, heparin, alemtuzumab, programmed death-1 inhibitors, abciximab, valproate, and quinine. 

Patients with leukemia, metastatic diseases, and bone marrow diseases, including myelodysplastic syndromes, myelofibrosis, aplastic anemia, megaloblastic anemia, myelophthisis, and Gaucher disease, can also exhibit thrombocytopenia. Other differentials include the rare possibilities of post-transfusion purpura and response to recent vaccinations.11 

Read more about ITP diagnosis

References

  1. Pietras NM, Pearson-Shaver AL. Immune thrombocytopenic purpura. In: StatPearls [Internet]. Treasure Island, FL: StatPearls Publishing; 2022. Updated May 10, 2022. Accessed October 17, 2022.
  2. Idiopathic thrombocytopenic purpura. John Hopkins Medicine. Accessed October 17, 2022.
  3. Idiopathic thrombocytopenic purpura (ITP) causes, symptoms and treatment. Children’s Hospital of Philadelphia. Accessed October 17, 2022.
  4. Zainal A, Salama A, Alweis R. Immune thrombocytopenic purpura. J Community Hosp Intern Med Perspect. 2019;9(1):59-61. doi:10.1080/20009666.2019.1565884
  5. Scott J. Causes, symptoms, and treatments of ITP and TTP. Verywell Health. June 1, 2021. Accessed October 17, 2022. 
  6. Miller DD, Krenzer JA, Kenkre VP, Rose WN. Sequential immune thrombocytopenia (ITP) and thrombotic thrombocytopenic purpura (TTP) in an elderly male patient with primary Sjogren’s syndrome: when in doubt, use the PLASMIC score. Case Rep Med. 2021;2021:6869342. doi:10.1155/2021/6869342
  7. Kuter DJ. Hemolytic-uremic syndrome (HUS). MSD Manual Professional Version. Updated September 2022. Accessed October 17, 2022.
  8. Justiz Vaillant AA, Gupta N. ITP-immune thrombocytopenic purpura. In: StatPearls [Internet]. Treasure Island, FL: StatPearls Publishing; 2022. Updated July 8, 2022. Accessed October 17, 2022.
  9. Boral BM, Williams DJ, Boral LI. Disseminated intravascular coagulation. Am J Clin Pathol. 2016;146(6):670-680. doi:10.1093/ajcp/aqw195
  10. Levi MM. Disseminated intravascular coagulation (DIC) differential diagnoses. Medscape. Updated August 23, 2022. Accessed October 17, 2022.
  11. Kessler CM. Immune thrombocytopenia (ITP) differential diagnoses. Medscape. Updated January 7, 2021. Accessed October 17, 2022.

Reviewed by Hasan Avcu, MD, on 10/30/2022.

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