Immune Thrombocytopenia (ITP)
Immune thrombocytopenia is an acquired immune-mediated platelet disorder causing isolated thrombocytopenia and a mucocutaneous bleeding phenotype; diagnosis is one of exclusion, and treatment is guided by bleeding risk, platelet count, comorbidity and treatment burden rather than the count alone.
Definition
Immune thrombocytopenia is an acquired immune-mediated disorder in which platelet destruction and impaired platelet production cause isolated thrombocytopenia after alternative causes have been considered. It is primary when no associated condition is identified and secondary when it accompanies an infection, autoimmune disease, lymphoproliferative disorder or drug exposure.
First principles
Immune clearance and impaired production both lower the count
Autoantibodies bind platelet surface glycoproteins, promoting splenic clearance, while immune effects on megakaryocytes reduce platelet production. This explains why ITP is not simply excessive splenic destruction and why treatments can either suppress immune clearance or increase platelet production.
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