Interestingly, we found that MMP-7, MMP-9, MMP-10, and MMP-12 were useful as diagnostic tools for identifying the presence of ILD in patients with RA and SSc (area under the curve (AUC): 0.8996, p < 0.0001, AUC: 0.7433, p = 0.0007, AUC: 0.6967, p = 0.0061, AUC: 0.7355, p = 0.0013, respectively, Fig. 3A, for RA-ILD+; and AUC: 0.8816, p < 0.0001, AUC: 0.9324, p < 0.0001, AUC: 0.7132, p = 0.0081, AUC: 0.7061, p = 0.0108, respectively, Fig. 3B, for SSc-ILD+, Additional File 2: Table S2). This evidence concerns the gene MMP9 and interstitial lung disease.