A Rare Presentation of Sjögren's Syndrome With Hypokalemic Periodic Paralysis Treated Based on Renal Biopsy Findings.

Hypokalemic periodic paralysis (HPP) is a rare but significant manifestation of Sjögren's syndrome, often associated with distal renal tubular acidosis (dRTA). We report a case of a 60-year-old man with recurrent HPP due to severe hypokalemia. Despite the absence of sicca symptoms, serological testing and glandular function assessment confirmed the diagnosis of Sjögren's syndrome. Laboratory findings revealed marked hypokalemia, metabolic acidosis, and excessive urinary potassium excretion, consistent with dRTA. Renal biopsy showed a combination of hypokalemia-induced tubular damage and autoimmune tubulointerstitial nephritis (TIN). Potassium and bicarbonate supplementation improved symptoms initially, but persistent tubular dysfunction required a reassessment of the treatment strategy. Steroid therapy was introduced 14 months after renal biopsy due to ongoing tubular dysfunction, leading to significant renal function improvement and discontinuation of potassium supplementation. This case highlights the importance of considering Sjögren's syndrome in patients with unexplained hypokalemic paralysis, even in the absence of sicca symptoms. Furthermore, it underscores the potential role of renal biopsy in distinguishing hypokalemia-induced tubular dysfunction from autoimmune TIN, guiding treatment decisions in complex cases of Sjögren's syndrome with renal involvement.