Thrombocytopenia: Causes and Classification

•    Decreased production: marrow failure, MDS, drugs, infections

•    Increased destruction: ITP, DIC, TTP, HUS

•    Sequestration: splenomegaly

•    Risk of bleeding ↑ when platelets < 50 × 10⁹/L

Thrombocytosis: Reactive vs Clonal

•    Reactive: infection, inflammation, iron deficiency, post-surgery

•    Clonal: essential thrombocythaemia, CML, PV

Platelet Function Disorders

•    Congenital: Glanzmann thrombasthenia, Bernard–Soulier syndrome

•    Acquired: antiplatelet drugs (aspirin, clopidogrel), uraemia

Heparin-Induced Thrombocytopenia (HIT)

•    Type 1: benign, non-immune, early

•    Type 2: immune-mediated (anti-PF4), thrombosis risk

•    Suspect: ↓ platelets >50% + thrombosis on heparin

•    Stop heparin, start alternative anticoagulant (e.g. argatroban)

Approach to Bleeding with Normal Coagulation Tests

•    Think platelet problem or vWD

•    Assess bleeding time, platelet count and function

•    Consider mild vWD, scurvy, Ehlers-Danlos, medications