Heparin-induced thrombocytopenia type II (HIT II) is a well documented, immune mediated severe adverse effect of heparin, caused by IgG (more rarely IgM) antibodies against the heparin/platelet factor 4 (PF4) complex, resulting in platelet activation and aggregation, endothelian activation, thrombin generation and eventually in thrombocytopenia and thrombotic events [1,2]. The gene discussed is PF4; the disease is Thrombocytopenia.