Acpa

Antimicrobial peptides are innate defence molecules — but in RA they become autoantigens, immune adjuvants and drivers of bone erosion. This review tracks LL-37, the defensins and the S100 proteins across five stages, from mucosal predisposition through to chronic synovitis, and makes the case that they amplify rather than initiate disease. Calprotectin already outperforms CRP and ESR for reflecting joint inflammation, yet no AMP-based agent has entered an RA trial since a phase II failure in 2019.

ACPA-positive and ACPA-negative RA take the same total time from first symptom to arthritis — but split it in mirror image. Seropositive patients reach the rheumatologist later and convert faster; seronegative patients arrive sooner and linger, leaving roughly twice as long an actionable window once they are in front of you. Each entity carries its own signature before arthritis exists.

Five-year data from the TREAT EARLIER trial show that a time-limited intervention (one glucocorticoid injection plus 12 months of methotrexate) in clinically suspect arthralgia produced durable benefit in ACPA-negative individuals at increased risk — RA in 9% vs 32%, NNT 4 — but nothing lasting in ACPA-positive individuals, splitting the at-risk phase into two diseases with two different answers.

A combined individual-patient-data analysis of the NORD-STAR and BeSt trials shows that where early RA is distributed carries prognostic signal: hand-dominant disease (JIP-Hand) predicts better treatment response and polyarthritis (JIP-Poly) worse — independent of sex and serology, and equally across csDMARDs and bDMARDs, with ACPA/RF showing no association with short-term activity response.