Polyautoimmunity in systemic lupus erythematosus: secondary Sjogren syndrome.

Background: Sjogren's syndrome (SS) is a chronic autoimmune disease characterized by lymphocytic infiltration of the exocrine glands. It can be associated with other connective tissue diseases, including systemic lupus erythematosus (SLE).

Objective: This study aimed to determine the incidence of secondary SS (sSS) in patients diagnosed with SLE (SLE-SS) and compare the clinical and serological features of SLE-SS to SLE only.

Methods: A retrospective observational study including patients diagnosed with SLE (SLICC criteria) seen at the Rheumatology Department between 1990 and 2020 was performed. A total of 453 SLE patients were assessed for fulfilment of the criteria for SS using the European questionnaire and Schirmer test, fluorescein staining/non-stimulated whole-salivary flow, anti-Ro/La antibodies, and lip biopsy. Anti-Ro/SSA and anti-La/SSB antibodies and rheumatoid factor (RF) were measured at entry and at SS assessment. SLE-SS was defined according to the American-European Consensus Criteria (AECC). SLE-SS was defined as a case that initially only fulfilled SLE classification criteria but which exhibited disease progression during follow-up and then met classification criteria for sSS.

Results: SLE-SS occurred in 11% of the SLE patients. In comparison to SLE-only patients, the SLE-SS group was older at inclusion and onset, and had a longer disease course. Sicca syndrome, oral ulcers, pulmonary involvement, and peripheral neuropathy were more frequent. Anti-SSA, anti-SSB, RF, and total IgG were higher in the SLE-SS group.

Conclusion: SLE-SS appears to be a subgroup of patients with distinct clinical and serologic features. The frequency of SLE-SS increases with age. Patients with SLE-SS have a higher frequency of oral ulcers, anti-Ro and anti-La antibodies, and a lower frequency of renal disease, anti-dsDNA antibodies, anti-SM, and lower C3 and C4 hypocomplementemia.