What is HIT?
Heparin-induced thrombocytopenia is an allergy-like reaction to heparin; the most widely used injectable anticoagulant (blood-thinner). Heparin-induced thrombocytopenia is caused by the body's development of antibodies to the complex of heparin and a blood protein called platelet factor 4 (PF4). It is characterized by a reduction in platelet count most typically occurring about 5 days after heparin exposure, and often leads to blood clotting. Heparin-induced thrombocytopenia and thrombosis syndrome, sometimes called HITTS, refers to a patient with heparin-induced thrombocytopenia and thrombosis (blood clotting). Since a high proportion of patients with HIT have thrombosis at diagnosis or will develop thrombosis within the first month following diagnosis, the distinction is becoming less relevant, and the condition is sometimes referred to as HIT syndrome.