Sjögren's syndrome associated with erosive rheumatoid arthritis alters its prognosis and long-term therapeutic response: a case–control study

10% of rheumatoid arthritis (RA) cases are associated to so-called secondary Sjögren's syndrome (SS). These RA cases have higher DAS, fewer remissions. Is this linked to a poor response to DMARDs (disease-modifying anti-rheumatic drugs)? No study has addressed this question to date. Does the association between secondary Sjögren's syndrome (SS) and rheumatoid arthritis (RA) affect the therapeutic response to DMARDs and long-term prognosis? We conducted a retrospective case–control study: 39 RA associated with SS was (anti-SSA antibodies and/or Chisolm stage III or IV) were compared to 39 isolated cases of erosive RA matched by age, duration of progression and gender. The DAS CRP was higher in the RA + SS group in patients with disease progression of 16 years: 2.6 (1.5–4.5) compared to the RA group: 1.6 (1.3–2.8) (p = 0.0001) while fewer patients were in remission: 61 vs. 92% (p = 0.002). A higher number of B DMARDs have been prescribed: RA + SS = 3.04 (1–7); RA = 1.7 (1–5) (p = 0.004). Anti-TNFs are less effective when RA is associated with SS: 30 vs. 70%. Conversely, Rituximab is more effective when RA is associated with SS: 80 vs. 30%. Erosive RA-related SS exacerbates the clinical course of the condition: higher DAS, fewer remissions. This is linked to reduced treatment efficacy: higher number of DMARDs prescribed, reduced efficacy of anti-TNF drugs. RA-related SS could modify sensitivity to biotherapies: lower percentage of remissions and resistance to anti-TNF drugs.