Background One of the main features of primary Sjögren's syndrome (pSS) is the polyclonal activation of B cells, leading to the synthesis of a large variety of autoantibodies.
Objectives The aim of this study is to describe the prevalence of atypical autoantibodies in patients with pSS from the SjogrenSER registry.
Methods SjogrenSER registry is a multicenter transversal study of pSS patients fulfilling European/American consensus criteria 2002. Patients were included by randomization from thirty-three Rheumatology Spanish departments. Data were collected by reviewing clinical records and interviewing the patients. Informed consent was obtained and local ethics committees approved the study. Variables were analysed by descriptive statistical methods, using means, medians, and rates. Chi-square was used to establish the statistical associations, being considered a p<0,05 as significant.
Results Four hundred and thirty-seven patients were included. Ninety-five percent of them were women. The median age of the cohort was 58 years. Twenty-three patients had AntiDNA (5.26%), 10 patients AntiSm (2.29%), 23 patients AntiRNP (5.26%) and 26 patients antiphospholipid antibodies (5.95%). Regarding AntiDNA+ patients, there were minimal non-significant differences in age at diagnosis and age at onset of symptoms compared to AntiDNA- patients (47 vs 50.5 years and 43.5 vs 46.5 years, respectively). The association with some systemic manifestation was only observed with joint involvement, which was significantly more frequent in AntiDNA+ patients (56.5% vs 34.2%, p=0.031). Regarding AntiSm+ patients, a significant negative association with AntiDNA antibodies was observed, being 70% of patients AntiDNA-; we also found a significant positive association with AntiRo and AntiLa, being 100% and 68% of patients AntiRo+ and AntiLa+ respectively. A significant negative association with lymphopenia was observed (no AntiSm+ patient had lymphopenia). AntiRNP+ patients showed a significant negative association with AntiDNA antibodies, being 80% of patients AntiDNA-, and a significant positive association with AntiRo, being 96% patients AntiRo+. A significant positive association was also observed with decreased C4 compared to AntiRNP- patients (28% vs 13.38%, p=0.025). Regarding patients with antiphospholipid antibodies, a significant negative association was observed with antiDNA antibodies, being 93% of patients AntiDNA-. A significant positive association with some systemic manifestation was only observed with the presence of anemia (44% vs 17.7%). A significant positive association with decreased C3 and C4 was also observed, compared with the AntiRNP- patients (C3 20% vs 13.67% and C4 33% vs 12.67%).
Conclusions More than 5% of pSS patients had antibodies characteristic of other autoimmune diseases. These atypical autoantibodies were significantly related to some pSS characteristic: antiSm, antiRNP and antiphospholipid antibodies were significantly related to the presence of antiRo, antiDNA antibodies were significantly related to joint involvement, antiphospholipid antibodies were significantly related to anemia, and antiRNP and antiphospholipid antibodies were significantly related to hypocomplementemia.
Disclosure of Interest None declared