Association between Rheumatoid Arthritis and other autoimmune diseases

Objectives: To determine the frequency of autoimmune diseases (AID) in Rheumatoid Arthritis (RA) patients and to compare this frequency between patients with and without RA or other rheumatologic AID. Methods: Multicenter, observational, analytical, retrospective study. Consecutive patients with diagnosis of RA (ACR/EULAR 2010) were included. Patients with initial diagnosis of primary ostearthritis (OA) were used as control group. Results: A total of 1549 patients were included: 831 RA (84% women, mean age 55.2 [±13.6]) and 718 OA (82% women, mean age 67 ([± 11.1]). The frequency of AID in the RA group was 22% (n=183). RA patients showed higher frequency of rheumatologic AID (9.4 vs 3.3%, p< 0.001), and lower frequency of non-rheumatologic AID than OA patients (15.3 vs 20.5%, p= 0.007). The most prevalent rheumatic AID was Sjögren’s Syndrome, which was more fre-quent in the AR group (87.2 vs 29.2%, p<0.001). The frequency of rheumatologic AID in RA patients was higher in those with erosive RA (11 vs 6.8%, p=0.048). Conclusion: The frequency of AID in RA patients was 22%. Rheumatologic AID were more frequent in RA patients, whereas non-rheumatologic AID prevailed in OA patients.