FAP and rheumatoid arthritis: Despite these interesting results and further potential diagnostic applications of FAP-directed PET imaging, for instance in chronic pancreatitis (Figure 3B), fibrosis of lung, liver and kidneys, sarcoidosis, RA and possibly also atherosclerosis, studies are warranted to assess the prognostic value of FAP(I)-directed PET as well as to determine whether it can be used to risk-stratify patients in these various inflammatory and fibrotic diseases.