[Ten questions related to heparin-induced thrombocytopenia]

Heparin-induced thrombocytopenia (HIT) is a potentially fatal, immune-mediated adverse drug reaction to heparin (both unfractionated and low molecular weight heparin) which is caused by the formation of IgG antibodies against an epitope composed by platelet-derived PF4 and heparin. Binding of IgG to PF4/heparin neoantigen induces platelet activation which may cause venous or arterial thrombosis, associated with thrombocytopenia. HIT diagnosis is based on both pre-test clinical probability evaluation and the detection of platelet activating antibodies. Laboratory diagnosis is based on immunologic and functional assays. When HIT is diagnosed any type of heparin should be stopped immediately and non-heparin alternative anticoagulant must be started in order to halt the pro-thrombotic process. Argatroban and danaparoid are currently the only drugs approved for HIT treatment. Bivalirudin and fondaparinux are also used for the treatment of this rare but severe condition.