Polyautoimmunity in Patients With Anticyclic Citrullinated Peptide Antibody-Positive and -Negative Rheumatoid Arthritis: a Nationwide Cohort Study From Denmark.

Polyautoimmunity as captured through the Danish National Patient Registry occurred in approximately 1 in 10 patients with RA at time of diagnosis regardless of anti-CCP status. In the years subsequent to the RA diagnosis, only a few and mainly anti-CCP-negative patients developed autoimmune disease.