Fibroblast activation protein (FAP) is a membrane-bound serine protease expressed almost exclusively on activated fibroblasts.9, 10, 11 Its expression is not encountered in healthy adult tissue but is seen after myocardial infarction as well as in a range of other heart muscle diseases.9, 10, 11, 12 FAP inhibitors (FAPIs) have been developed and modified to facilitate positron emission tomography (PET) imaging of fibroblast activation and fibrosis activity.13 The gene discussed is FAP; the disease is myocardial infarction.