Among the five variables, including age, serum levels of ferritin, IL-18, and MMP-3 level, and days of illness at the onset of arthritis, only ferritin showed a significant difference among interval fever-onset, continued fever-onset/non-biologic, and continued fever-onset/biologic patients (Figures 3A,B and Supplementary Figure 2). Here, MMP3 is linked to arthritic joint disease.