To estimate the prevalence and investigate the clinical features and the outcome of clinically significant renal involvement in a large cohort of patients with primary Sjögren's syndrome (SS).
Among 715 patients who met the American-European Consensus Group criteria for primary SS, those with clinically significant renal involvement were identified and their clinical and immunologic features were recorded. The prognosis in patients with primary SS with renal involvement was assessed by the clinical appearance of any of the following major outcomes: death, hemodialysis, chronic renal failure (CRF), and lymphoma. Kaplan-Meier analysis was applied to compare death rates between patients without and those with renal involvement.
Thirty-five patients with primary SS (4.9%) had clinically significant renal involvement, representing a total followup time after renal diagnosis of 252.2 person-years. Thirteen patients (37.1%) had interstitial nephritis alone, 17 patients (48.6%) had glomerulonephritis (GN) alone, and 5 patients (14.3%) had both entities. Nine patients died (25.7%), 11 developed CRF (including 4 requiring chronic hemodialysis) (31.4%), and 9 developed lymphoma (25.7%). The overall 5-year survival rate was 85%. Kaplan-Meier analysis showed statistically significant reduced survival for patients with primary SS with renal involvement compared to those without renal involvement (P < 0.0001 by log rank test), with GN patients displaying increased mortality. Eight of 9 reported deaths (89%) and 8 of 9 lymphomas (89%) were observed among patients with GN.
The long-term prognosis varies for patients with primary SS who have clinically significant renal involvement. Patients with interstitial nephritis display a favorable prognosis, while patients with GN are at high risk of developing lymphoma and have poor survival.