Primary Sjögren syndrome-associated acute interstitial nephritis and type 3 renal tubular acidosis in a patient with thin basement membrane nephropathy: A case report

INTRODUCTION: The kidney is one of the common extraglandular sites involved in primary Sjögren syndrome (pSS), with chronic tubulointerstitial nephritis (TIN) the most common pathology type. Renal involvement in pSS often presents as chronic TIN accompanied by type 1 or 2 renal tubular acidosis (RTA). Description of renal involvement as acute TIN with type III RTA in pSS has been rarely reported. PATIENT CONCERNS: A 37-year-old woman was admitted with complaints of dry mouth, dry eyes, and progressive muscle weakness for 17 months. Two months before admission, the patient had a blood potassium level of 1.7 mmol/L. DIAGNOSIS: Further tests confirmed pSS and type III RTA. Renal biopsy demonstrated acute TIN and thin basement membrane nephropathy (TBMN). INTERVENTIONS: Full-dose corticosteroid (1 mg/kg/day) and cyclophosphamide (100 mg/day) were applied. OUTCOMES: The creatinine levels of the patient decreased 0.28 mg/dL (1.18–0.90 mg/dL) during 3-month follow-up. CONCLUSIONS: We reported a patient with pSS-associated kidney injury, presenting as acute TIN with type 3 RTA and TBMN. This case increases the awareness of a rare manifestation of pSS-associated kidney injury. In pSS-associated acute TIN, cyclophosphamide combined with full-dose corticosteroids may achieve good outcomes.