Idiopathic Thrombocytopenic Purpura
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- Idiopathic thrombocytopenic purpura (ITP) is thrombocytopenia without apparent cause or abnormalities in other celllines.
- Incidence is ∼2–5/100,000/yr—may be an underestimate owing to undetected, subclinical cases.
- Acute ITP:
- 1/2 of cases involve children.
- 80% of children recover within 8 wk with or without therapy.
- Adult recovery is delayed and requires specific therapy to achieve remission.
- Chronic ITP:
- Occurs mostly in adults
- Young women are most susceptible in adult onset ITP
- Characterized by variable response to corticosteroids and other immune suppressants
- 60–70% respond to splenectomy
- Chronic refractory ITP:
- Platelet counts may often wax and wane.
- Often do not respond to therapy
- No clear optimal course of treatment
- ITP appears to run in families, as do variations in response to corticosteroids for treatment.
- Autoantibodies produced by B cells and plasma cells cause immune-mediated destruction of circulating platelets
- Macrophages in spleen and liver mediate destruction of platelets via IgG autoantibodies
- IgM and IgA rarely have been seen
- Some patients do not possess autoantibodies, suggesting a role for T cell-mediated cytotoxicity.
- C3 and C4 complements have also been shown to play a role in patients that lack autoantibodies
- Poor platelet production may also play a role especially in chronic or refractory cases of ITP
- Eradication of Helicobacter pylori can sometimes be associated with platelet recovery (unclear mechanism).