What is the clinical hallmark of heparin-induced thrombocytopenia and its management?

• A. Sudden platelet drop 5–14 days after heparin with risk of thrombosis; stop heparin and start a nonheparin anticoagulant (eg, argatroban)
• B. Gradual platelet drop with bleeding; continue heparin
• C. Platelet count rises after heparin
• D. There is no risk of thrombosis with HIT

Answer: (A)

HIT is an immune-mediated reaction where antibodies form against the heparin–platelet factor 4 complex, causing platelet activation and a prothrombotic state. The clinical hallmark is a sudden drop in the platelet count occurring about 5–14 days after starting heparin, with a substantial risk of new thrombosis even though bleeding might not be prominent. The correct management is to stop all heparin immediately and switch to a nonheparin anticoagulant such as a direct thrombin inhibitor (for example, argatroban). Warfarin is avoided until platelet counts recover, and platelet transfusions are generally avoided unless there is life-threatening bleeding. The other descriptions don’t fit HIT: a gradual drop with ongoing heparin isn’t typical, a platelet rise after heparin is the opposite of what happens, and there is indeed a real risk of thrombosis in HIT.