HC; healthy controls, UA; undifferentiated arthritis, CA; crystal arthropathy, PsA; psoriatic arthritis, SLE; systemic lupus erythematosus, ACPA; anti-cyclic citrullinated protein antibodies, RA; rheumatoid arthritis, DAS; disease activity score, RF; rheumatoid factor, ESR; erythrocyte sedimentation rate, CRP; C-reactive protein, sDMARD; synthetic disease modifying anti-rheumatic drug. The gene discussed is CRP; the disease is crystal arthropathy.