Coexistence of Sjögren’s Syndrome-associated Interstitial Nephritis and Hypokalemic Nephropathy in a Patient with Distal Renal Tubular Acidosis

A 42-year-old woman presented with muscle weakness and hypokalemic distal renal tubular acidosis (dRTA). Investigations revealed concurrent Sjögren’s syndrome (SS) and Hashimoto’s thyroiditis contributing to hypokalemic dRTA. A renal biopsy revealed focal tubulointerstitial nephritis (TIN) suggestive of SS-related renal involvement, along with distinctive ischemic glomerular changes and tubular alterations consistent with hypokalemic nephropathy. Rapid improvement in tubular injury markers and hypobicarbonemia followed potassium supplementation, suggesting that hypokalemia contributed to proximal tubular injury. This case underscores the diagnostic challenge posed by the simultaneous presence of TIN and hypokalemic nephropathy, potentially masking hypokalemic nephropathy in patients with hypokalemic dRTA secondary to SS-TIN.