Similarities and differences between primary and secondary Sjögren's syndrome.

OBJECTIVE

To define the clinical, serological, and histopathological characteristics of primary (pSS) and secondary Sjögren's syndrome (SS).

METHODS

Fifty subjects with pSS and 300 with connective tissue diseases (CTD; systemic lupus erythematosus 100, rheumatoid arthritis 100, scleroderma 100) were selected randomly from our patient registry. Selected patients were assessed for fulfillment of the American-European Consensus Group criteria for SS using a 3-phase approach: screening (European questionnaire, Schirmer-I test, wafer test), confirmatory (fluorescein staining test, nonstimulated whole salivary flow, anti-Ro/La antibodies), and lip biopsy (H&E and immunohistochemical staining for anti-CD20 and anti-CD45RO scored by morphometry).

RESULTS

All patients with pSS and 65 with CTD met criteria for SS. Oral symptoms (pSS = 92% and secondary SS = 84%; p = 0.02), parotid enlargement (pSS 56%, secondary SS 9.2%; p < 0.001), and higher prevalence (pSS 82%, secondary SS 41%; p < 0.001) and titers of anti-Ro/La antibodies were more common in pSS. Extraglandular manifestations were similar in both groups, except for Raynaud's phenomenon, which was more common in those with secondary SS (pSS 16% vs secondary SS 41%; p = 0.001). These results remained after 3 different sensitivity analyses. The prevalence of focal infiltration was also similar in both SS varieties; however, a higher B:T cell ratio and higher expression of CD20 cells (2922 vs 607.5 positive cells; p < 0.001) were observed in pSS.

CONCLUSION

A higher frequency of oral symptoms and parotid enlargement and stronger B cell activity (autoantibody production and lymphocyte infiltration) were observed in pSS. Whether these results reflect a true difference between the 2 disease entities or derive from underlying variables remains uncertain.