We used Pearson’s correlation analysis to analyze the relationship between FVC or DLCO and galectin-9 expression levels in the serum of SSc patients, demonstrating a strong negative correlation with FVC but a weaker correlation with DLCO: FVC vs. galectin-9: r = − 0.737; DLCO vs. galectin-9: r = − 0.446 (mean FVC: 71.9 ± 14.3%, mean DLCO: 52.2 ± 19%, mean galectin-9 level: 31153 ± 18,832 pg/ml). The gene discussed is LGALS9; the disease is systemic sclerosis.