In particular, while catalase (CAT) activity showed only a tendency to be lower in SSc cells compared to the healthy counterparts (p = 0.0938), and its level was not influenced by the presence of H2O2 and/or sildenafil (p > 0.05), the analysis of superoxide dismutase (SOD) activity highlighted distinct and significant differences between the two groups. Here, CAT is linked to systemic sclerosis.