Objectives: To study the clinical and laboratory profile evolution, as well as morbidity and mortality impact, of primary Sjögren's syndrome (pSS), in a large cohort of patients followed-up longitudinally.

Methods: We studied the evolution of the clinical picture and laboratory profile of pSS, the incidence and predictors for systemic sequelae, and the impact of pSS on overall survival in a prospective cohort study of 261 patients with pSS. Analyses included calculation of incidence rates, Cox proportional hazards predictive models, and estimation of standardized mortality ratios (SMRs) compared with the general Greek population, adjusting for age and sex.

Results: Glandular manifestations of the syndrome were typically present at the time of diagnosis. Systemic manifestations such as arthritis, Raynaud's phenomenon, purpura, interstitial nephritis, and liver involvement, as well as the serological profile, also did not change substantially during subsequent follow-up. Incidence rates for peripheral neuropathy, glomerulonephritis, and lymphoproliferative disorders were 3.3, 6.6, and 12.2 per 1,000 person-years, respectively. Glomerulonephritis and lymphoma tended to co-exist in the same patients (relative risk, 34.0; P < .0001). The development of lymphoproliferative disorders was associated with low levels of C4 complement (relative risk, 7.5; P = .0016), the presence of mixed monoclonal cryoglobulins (relative risk, 7.9; P = .0012), and purpura (relative risk, 3.9; P = .037). Low levels of C4 was the strongest predictor for mortality after adjusting for age (relative risk, 6.5; P =.0041). Patients with pSS had an SMR of 2.07 (95% CI, 1.03 to 3.71). However, when patients with adverse predictors were excluded, the mortality rate was identical to that of the general population (SMR 1.02).

Conclusions: The initial presentation of pSS determines subsequent outcome. Purpura, decreased C4 complement levels, and mixed monoclonal cryoglobulinemia are adverse prognostic factors. The overall mortality of patients with pSS compared with the general population is increased only in patients with adverse predictors.