Clinically significant renal involvement in primary Sjögren's syndrome is associated with important morbidity: data from the Spanish Sjögrenser cohort.

Objectives: To investigate the prevalence, associated factors, and effects of primary overt renal disease on morbidity in patients with primary Sjögren's syndrome (pSS).

Methods: All patients in the Sjögrenser (registry of adult pSS patients of the Spanish Society of Rheumatology) cohort were retrospectively investigated for the presence of clinically significant renal involvement directly related to pSS activity.

Results: Of the 437 patients investigated, 39 (9%) presented overt renal involvement during follow-up. Severe renal disease necessitating kidney biopsy was relatively rare (2%). Renal involvement may complicate pSS at any time during the disease course and is associated with severe disease (indicated by higher scores of involvement, activity, and damage), systemic multiorgan involvement, and a higher frequency of lymphoma. Multivariate analysis showed that older age (odds ratio [OR] 1.03, 95% confidence interval [CI] 1.00-1.07), higher European League Against Rheumatism Sjögren's Syndrome Disease Activity Index scores (OR 1.1, CI 1.03-1.18), serum anti-La/SSB positivity (OR 6.65, CI 1.41-31.372), and non-vasculitic cutaneous involvement (OR 5.47, 1.03-29.02) were independently associated with this complication. Chronic renal failure developed in 23 of 39 patients (59%); only 1 of them progressed to end-stage renal disease necessitating renal replacement therapy. Patients with overt renal disease showed higher Sjögren's syndrome disease damage index scores, higher rates of hospitalisation due to disease activity and higher rates of clinically relevant comorbidities.

Conclusions: Overt renal involvement in pSS is not uncommon. Although it usually shows a favourable prognosis, is associated with significant morbidity.