Increased serum levels of MMP-7, MMP-9, MMP-10 and MMP-12 were found in patients with RA-ILD+ and SSc-ILD+ in relation to RA-ILD- and SSc-ILD- patients, respectively (RA: p < 0.0001, p = 0.0029, p = 0.0369, p = 0.0107, Fig. 1A; and SSc: p = 0.0004, p < 0.0001, p = 0.0068, p = 0.0064, Fig. 1B; respectively). This evidence concerns the gene MMP9 and rheumatoid arthritis.