Healthy individuals exhibited markedly higher ISM1 concentrations (mean ± SD, 972 ± 809 ng/L; median (IQR), 678 (710) ng/L) compared to RA patients with moderate-to-high disease activity defined by DAS28-CRP ≥ 3.2 (mean ± SD, 315 ± 125 ng/L; median (IQR), 311 (184) ng/L; p < 0.001), with a very large effect size (Cohen’s d = 1.34). This evidence concerns the gene ISM1 and rheumatoid arthritis.