OP = osteoporosis, SD = standard deviation, IQR = interquartile range, RA = rheumatoid arthritis, RF = rheumatoid factor, ACR = American College of Rheumatology, DAS-28 ESR = disease activity score 28 swollen and tender joint count using the erythrocyte sedimentation rate, ACPA = anti-citrullinated protein antibody. The gene discussed is PRTN3; the disease is osteoporosis.