#6663 PRIMARY SJöGREN SYNDROME WITH BIOPSY PROVEN RENAL INVOLVEMENT: A SINGLE CENTER EXPERIENCE
Authors: Tinoco Adria , Arce Yolanda , Guasch Anna Domínguez , Khalil Jonas El Bachouti , Bardaji Beatriz , Aliaga Carolt Arana , Barros Xoana , Marco Helena , Encarnación Montserrat Díaz 
Published: June 2023

Abstract

Background and Aims
Primary Sjögren's syndrome (pSS) is a chronic systemic autoimmune disease, characterized by inflammation and destruction of the exocrine glands and the involvement of multiple organs. A wide variety of kidney manifestations associated with pSS have been described. The prevalence of kidney involvement is not clear. Our aim was to describe the renal involvement of patients with pSS diagnosed by kidney biopsy (KB). We also analyzed the clinical manifestations, laboratory and immunological characteristics, clinical outcomes and treatments received in patients with pSS referred to a specialized kidney centre.

Method
Observational, retrospective study of adult patients (age &gt; 18 years) diagnosed with pSS (EULAR criteria) referred and treated at a kidney referral centre (Fundació Puigvert) in Barcelona, Spain. We collected data from the clinical records registry including demographic variables, laboratory parameters, biopsy results and adverse outcomes, defined by the need of renal replacement therapy (RTT) and/or death. Absolute frequencies, percentages, means and standard deviations were used for statistical analysis. Multivariate analysis was performed as appropriate in SPSS V28.0

Results
A total of 27 patients with pSS underwent KB from January 1994 to July 2022; all patients were female, with a median age of 58.4 years (SD ±12.4); 85% were Caucasian. The mean baseline glomerular filtration rate (eGFR) was 65.9 mL/min (SD ±16) (before nephrologist referral), with 8 of 27 patients (29.6%) having eGFR less than 60 mL/min at baseline. The main indication for nephrological evaluation was acute kidney injury (AKI) (63%), followed by the presence of non-nephrotic proteinuria with dysmorphic haematuria (29.6%). The most common finding in KB was acute interstitial nephritis (AIN) (55.6%), as an isolated AIN kidney lesion in twelve patients (44.4%). Mild interstitial nephritis was noted in the context of a predominant glomerular lesion in three other patients (one membranoproliferative glomerulonephritis, one IgA nephropathy and one AA amyloidosis). Nine patients (33.3%) had glomerular lesion (see Table 1). In 18.5% of patients, the diagnosis of pSS was made after the renal biopsy. The percentage of patients receiving ACEI/ARB was 77.8%. A total of 25 patients received some type of immunosuppression (IS). Corticosteroids being the most frequently used (77.8%), followed by the combination IS treatment (44%) and rituximab (33.3%). At the time of the KB, the mean eGFR was 46.3 mL/min (SD ±24), compared to eFGR of 45.2 mL/min (SD ±22) one-year after KB. During follow-up, seven patients (25.9%) required RRT and three (11.1%) died from non-renal causes, mainly by infections associated with immunosuppression. Factors associated with adverse renal outcomes were AKI (p = 0.01), baseline eGFR CKD-EPI less than 60 mL/min (p = 0.005), presence of anti-Ro60 antibodies (p = 0.046), use of plasmapheresis (p = 0.013), use of cyclophosphamide (p = 0.013) and the presence of tubulointerstitial atrophy with glomerular sclerosis on kidney biopsy (p = 0.010).

Conclusion
Our study included a larger cohort than previously reported before in a single centre. In our cohort of patients with pSS who were evaluated by KB, AIN was the leading cause of renal involvement, as has been seen in other studies. The presence of eGFR below 60 mil/min at baseline and the finding of chronicity in the KB are associated with an adverse outcome, as well as is the presence of AKI. Early referral to nephrologist may be important for prognosis, and KB is necessary for accurate diagnosis of kidney involvement to allow targeted treatment.