[Epidemiology of primary Sjörgren's syndrome]

Abstract

According to the classification criteria of the American-European Consensus Group (AECG), the prevalence of primary Sjögren's syndrome (pSS) of about 0.2% in the adult population and a yearly incidence of 4/100.000 in the general population are far lower than previously assumed. Moreover, the repeatedly reported male/female ratio of 1:9 seems to lie more in the range of 1:20. Male pSS patients show fewer immunological, histopathological or sialographic findings and organ involvement. Information on age at disease onset has also changed over the last decade. Recent studies indicate an onset age of approximately 45 years as compared to 56 in earlier studies of the last decade. Patients with an early disease onset are more frequently positive for rheumatoid factor (RF) and/or anti-Ro/SS-A. These patients also seem to have a higher risk of developing hypocomplementemia or lymphadenopathy. As compared to earlier cohorts, the introduction of the rather specific AECG criteria will probably result in the participation of fewer men, younger patients in general and of more seriously ill patients in future cohorts. The change in the spectrum of pSS patients obviously reflects the altered classification criteria since the AECG criteria require anti-Ro/La positivity and therefore exclude a high number of patients with other immunological markers who also show severe sicca symptoms and organ involvements. About 5%-10% of pSS patients in rheumatological care suffer from severe extraglandular manifestations, which generally occur soon after disease onset. In particular, palpable purpura, hypocomplementemia, cryoglobulinemia and lymphoma are associated with increased mortality. In Germany, approximately one tenth of Sjögren syndrome patients receive specialized rheumatological care. There is still insufficient knowledge about the vast majority of pSS patients who are not treated by rheumatologists. These patients, as well as all those who, according to the AECG criteria, are not classified as having pSS either due to anti-Ro/La negativity or having secondary Sjögren's syndrome, probably add up to at least 0.4% of the adult population which, at present, suffers from considerable immunopathologic sicca symptoms.