Paper I
Question
Immune thrombocytopenic purpura (ITP).
Answer
Immune thrombocytopenic purpura (ITP) is an autoimmune disorder characterized by isolated thrombocytopenia due to antibody-mediated platelet destruction.
Pathogenesis
- Autoantibodies (usually IgG) directed against platelet surface glycoproteins (commonly GpIIb/IIIa)
- Antibody-coated platelets are recognized and destroyed by splenic macrophages (Fc receptor-mediated phagocytosis)
Types
- Acute ITP: Common in children, often follows a viral infection, usually self-limiting
- Chronic ITP: More common in adults (especially women), insidious onset, persistent course
Clinical features
- Mucocutaneous bleeding — petechiae, purpura, epistaxis, gum bleeding, menorrhagia
- No splenomegaly (typically)
Laboratory findings
- Isolated thrombocytopenia (other cell lines normal)
- Peripheral smear: reduced platelets, may show large platelets (megathrombocytes)
- Bone marrow: normal to increased megakaryocytes (compensatory)
- Bleeding time prolonged; PT/aPTT normal
- Anti-platelet antibody testing may be positive (not routinely required for diagnosis — a diagnosis of exclusion)
Treatment
- Corticosteroids (first-line)
- IV immunoglobulin (for rapid platelet rise, e.g., before surgery/severe bleeding)
- Splenectomy (refractory/chronic cases)
- Thrombopoietin receptor agonists (refractory cases)