CRP and ankylosing spondylitis: Circulating IL-37 levels have been found to positively correlate with levels of CRP and/or ESR in patients with rheumatoid arthritis (18, 21–23), systemic lupus erythematosus (30), adult-onset Still’s disease (69, 70), ankylosing spondylitis (25), gout (71), and osteoarthritis (72), as well as in patients with chronic heart failure (38).