Tanner S, Dufault B, Smolik I, et al. - Indigenous North American people were examined for the incidence of inflammatory arthritis and autoantibody prevalence. Researchers systematically monitored unaffected relatives of Indigenous North Americans with rheumatoid arthritis (RA) from central Canada and Alaska from 2005 to 2017. Screening for rheumatoid factor (RF) and anti–citrullinated protein antibodies (ACPAs) was done at every visit, and ACPA fine specificity was assessed in a subset using a custom multiplex assay. Observations revealed the development of inflammatory arthritis in 18 of 374 relatives (4.8%) during follow-up (after a mean ± SD of 4.7 ± 2.4 years), yielding a transition rate of 9.2 cases/1,000 person-years. At baseline, seronegativity was reported in 30% of those who developed inflammatory arthritis, however, at inflammatory arthritis onset, all were seropositive. This cohort of at-risk relatives of Indigenous North Americans with RA displayed a high incidence of inflammatory arthritis, however, inflammatory arthritis did not develop in a large proportion of autoantibody-positive individuals. Furthermore, these individuals reverted back to an autoantibody-negative state.