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Primary Sjögren's syndrome (pSS) is a chronic autoimmune systemic disease with an estimated prevalence of 0.01 to 3%, characterized by the involvement of exocrine glands. Renal involvement occurs in less than 10%. Tubulointerstitial nephritis (TIN) is one of the commonly found abnormalities in renal biopsy and renal tubular acidosis (RTA) may be present.
The objective is to report a case series with diagnosis of pSS and renal involvement. We report 5 patients with pSS with renal features at onset; renal biopsy was performed, except for one pregnant patient.
All 5 patients were female, with an average age of 21.6 years. All patients had kidney involvement as initial manifestation of pSS. Two of them (40%) were pregnant at the time of diagnosis. The average baseline serum creatinine was 3 mg/dl, with an estimated glomerular filtration rate by CKD-EPIcr (eGFR) of 46.2 ml/min/1.73m². Two patients (40%) required renal replacement therapy (RRT) during their hospitalization, and three (60%) had RTA at the time of diagnosis. All kidney biopsies performed reported TIN. Glomerular injury was reported as focal segmental glomerulosclerosis observed in just one patient (20%). All patients were treated with prednisone and hydroxychloroquine, pregnant patients also received azathioprine and just one patient (20%) required maintenance renal replacement therapy.
This case series shows 5 patients with pSS with kidney disfunction as an unusual presentation. Acute or chronic tubulointerstitial nephritis (TIN) was found, in all patients which correlates with the literature. The age of presentation is below the average age at which SS is typically diagnosed. Renal manifestations in SS exhibit systemic symptoms that lead patients to seek medical attention, ultimately leading to the primary diagnosis of Sjögren's syndrome.