Onset of rheumatoid arthritis after COVID-19: coincidence or connected?

COVID-19, caused by SARS-CoV-2, can lead to severe inflammation and has been suggested to induce autoimmune phenomena. Multiple studies have reported autoantibodies in patients with COVID-19, particularly anti-cardiolipin, anti-β2-glycoprotein I and antinuclear antibodies.1 2 Anti-citrullinated protein antibodies (ACPA) and flaring of rheumatoid arthritis (RA) after SARS-Cov-2 infection have also been described.1 3 However, it is unclear how often ACPA occur after COVID-19 and whether they differ from ACPA normally found in patients with RA . We have therefore performed a detailed investigation into ACPA positivity after COVID-19. To determine the seroprevalence of ACPA after COVID-19, ACPA was measured using routine tests or in-house ELISA in 61 patients visiting the post-COVID-19 outpatient clinic of the Leiden University Medical Center 5 weeks after hospitalisation. None of the patients tested positive for ACPA, except two patients previously diagnosed with ACPA-positive RA. Thus, we could not observe an increase in ACPA positivity after COVID-19. Furthermore, we identified five patients across various Dutch rheumatology clinics presenting with polyarthritis compatible with RA after SARS-CoV-2 infection. To study the impact of COVID-19 on disease presentation, we closely examined their clinical phenotype and autoantibody characteristics (online supplemental table S1). All had suffered from moderate-to-severe COVID-19. On average, joint complaints started 6.6 weeks after infection, although two patients reported symptoms before infection. Four of five patients fulfilled the …