Among 90 consecutive patients with idiopathic inflammatory myopathy, the 12 patients that were tested positive for ACPA (including only 2 patients with anti-ARS) did not show any clinical or biological differences compared with ACPA-negative patients, except for rheumatoid factor positivity.21 This discrepancy with the present findings may be the result of the small number of ACPA–ASS patients, differences in diagnostic test specificity,38 and/or limited follow-up. Here, PRTN3 is linked to idiopathic inflammatory myopathy.