Paper I
Question
Immune thrombocytopaenic purpura
Answer
Immune thrombocytopenic purpura (ITP) is an autoimmune disorder characterized by isolated thrombocytopenia from antibody-mediated platelet destruction.
Pathogenesis
- Autoantibodies (usually IgG) directed against platelet surface glycoproteins (commonly GpIIb/IIIa)
- Antibody-coated platelets are prematurely destroyed by splenic macrophages via Fc receptor-mediated phagocytosis
- Antibodies may also impair megakaryocyte function, contributing to reduced platelet production in some cases
Types
- Acute ITP: Common in children, often post-viral, usually self-limiting
- Chronic ITP: More common in adults (especially women), insidious onset, persistent
Clinical features
- Mucocutaneous bleeding — petechiae, purpura, epistaxis, gum bleeding, menorrhagia
- Spleen typically not palpable/enlarged
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 (diagnosis of exclusion)
Treatment
- Corticosteroids (first-line)
- IV immunoglobulin (rapid platelet rise)
- Splenectomy (chronic/refractory cases)
- Thrombopoietin receptor agonists (refractory cases)