Renal involvement in Sjogren's syndrome: predictors and impact on patient outcomes

Renal disease in primary Sjogren's Syndrome(pSS) occurs as tubulointerstitial nephritis(TIN) or glomerulonephritis(GN). Data from India on pSS are sparse and even less on nephritis.We studied the prevalence and impact of renal disease on patient outcomes. We reviewed 179 (F:M 12.7:1, age 41.7 +/- 12.9 years) patients of pSS from records at a single centre from 2000 to 2020. Data on nephritis, clinical and laboratory variables were collected from baseline visit. Outcomes studied were chronic kidney disease(CKD) and death. We identified predictors of nephritis and rising creatinine on follow-up.Fifty-four (30.17%) patients had nephritis. Their mean age was 40.19 +/- 13.28 years with 157.3 person-years follow-up. Vasculitis (OR 2.33, 1.02-5.3), fatigue (OR 3.29, 1.63-6.65), ANA positivity (OR 7.79, 1-60.62), anti-Ro52 (OR 2.74, 1.18-6.39), anti-La (OR 2.13, 1.1-4.14), both Ro and La (OR 2.4, 1.23-4.69) and lymphopenia (OR 2.27, 1.16-4.41) predicted nephritis on univariate analysis. On multivariate analysis, only fatigue (OR 2.83, 1.22-6.57) and an interaction between polyarthritis and vasculitis (OR 9.17, 1.15-72.96) was associated with nephritis. Creatinine at one (1.6 +/- 1.17 mg/dL vs. 0.8 +/- 0.2 mg/dL) and 2 years (1.62 +/- 1.19 mg/dL vs. 0.8 +/- 0.2 mg/dL) follow-up was higher in the nephritis group. Baseline haematuria, leukocyturia, 24 h urinary protein and thrombocytopenia were independent predictors of rising creatinine. Six patients died and 10 developed CKD. Event-free (death or CKD) survival was 89.1% at 5 years. Patients with nephritis had worse event-free survival.Our cohort had a younger age of onset of Sjogren's syndrome and a higher prevalence of nephritis than previously reported. Fatigue, polyarthritis and vasculitis at baseline predicted the development of nephritis. Nephritis was associated with a higher probability of death or CKD.