Immune Thrombocytopenic Purpura (ITP)

Summary

ITP, short for immune thrombocytopenic purpura, is a disease characterized by the autoimmune destruction of platelets. Specifically, patients with ITP produce antibodies against Gp2b/3A receptors on the surface of platelets. These antibodies mark the platelets for later destruction in the spleen. The disease is often associated with systemic lupus erythematosus, various viral infections, cancers, and may rarely be seen as a result of taking certain drugs. The primary clinical symptom of ITP is bleeding, especially from the skin and mucous membranes. Laboratory tests reveal decreased platelet counts, increased megakaryocyte activity in the bone marrow, and increased bleeding time. Finally, ITP may be treated using steroids, intravenous immunoglobulins, rituximab, as well as by performing a splenectomy.

Key Points

• Immune Thrombocytopenic Purpura (ITP)
  • Pathogenesis
    • Destruction of normal platelets by spleen
      • Usually due to anti-GpIIb/IIIa antibodies
      • Splenic macrophages target and phagocytose platelets
      • Idiopathic or secondary to autoimmune disorders (e.g. SLE), viral illnesses (e.g. HIV, HCV), malignancy (e.g. CLL), or drug reactions
  • Presentation
    • Mucocutaneous bleeding
      • Gingival bleeding, menorrhagia, petechiae, epistaxis, easy bruising
  • Diagnosis
    • Decreased platelet count (thrombocytopenia)
      • Quantitative defect in platelets; quality of platelets is unaffected
      • Isolated thrombocytopenia is often the only symptom of disease
    • Increased megakaryocytes on bone marrow biopsy
      • Intact compensatory response to platelet destruction
    • Increased bleeding time
      • Due to decreased platelet count
  • Treatment
    • Steroids
    • IVIG
    • Rituximab
    • TPO receptor antagonists (e.g. eltrombopag, romiplostim)
    • Splenectomy for refractory cases