Kidney Stones, Proteinuria and Renal Tubular Metabolic Acidosis: What Is the Link?

Kidney stone disease represents a rare cause of chronic kidney disease (2–3%) but has severe clinical consequences. Type 1 renal tubular acidosis is a strong lithogenic condition mainly related to primary Sjögren syndrome. This study aimed to illustrate an unusual presentation of Sjögren syndrome to improve the knowledge about rare kidney stone diseases, and to provide clues for the diagnostic approach in this specific condition. We report the case of a 35-year-old Indian woman with severe nephrocalcinosis and chronic kidney disease with tubular proteinuria who presented for metabolic assessment. We found advanced chronic kidney disease, low serum bicarbonate, permanent alkaline urine with pH at ~7.1, and severe hypocitraturia corresponding to type 1 renal tubular acidosis. The erythrocyte sedimentation rate was high. Serological screening for HAV, HBV, HCV, HIV, EBV was negative and complement was normal. Autoimmune screening showed antinuclear antibodies (>1/1.280) with anti-SSA, anti-SSA/Ro52 and anti-SSB antibodies. Genetic testing excluded an inherited cause of renal tubular acidosis. A renal biopsy showed moderate chronic tubulo-interstitial nephritis without any glomerular involvement. Primary Sjögren syndrome with significant renal involvement was considered, and corticosteroids were then subsequently initiated in combination with potassium citrate with vitamin D substitution. Only partial improvement was observed in electrolytes disturbance. After 15 months, her renal function remained stable. In conclusion, nephrocalcinosis could be the first manifestation of severely impacting diseases such as primary Sjögren syndrome. Chronic kidney disease, bilateral nephrocalcinosis, and metabolic acidosis can be linked through type 1 renal tubular acidosis. Therefore, autoimmune screening for Sjögren syndrome should be considered in such cases.