. Post discharge, he developed polyarthritis, and laboratory tests revealed positive results for rheumatoid factor (RF) and anti-citrullinated protein antibodies (ACPA). He was diagnosed with seropositive RA, and his symptoms improved with corticosteroid therapy. Retrospective review of positron emission tomography scans performed before admission revealed inflammatory uptake in multiple joints, suggesting a preclinical phase. This case suggests that acute respiratory infection may accelerate the transition from latent autoimmunity to clinically overt RA, highlighting the diagnostic value of RF and ACPA testing in new-onset arthritis after infection.
Arai et al. (Wed,) studied this question.