CASP4 and systemic sclerosis: This profibrotic branch mostly exists in SSc-ILD lungs, but not in healthy lungs, and expresses ferroptosis-related genes (ferroptosis-resistant genes: GPX4 and NR4A1 [57]; pro-ferroptotic genes: NCOA4 and SAT1 [58]); and pyroptosis drivers (CASP4 and GSDMD) (Fig. 5E).