Light Chain Proximal Tubulopathy in a 59-Year-Old Woman with Sjögren’s Syndrome: A Case Report and Review of the Literature

Light chain proximal tubulopathy (LCPT) is a rare form of monoclonal gammopathy of renal significance (MGRS), characterized by the deposition of monoclonal light chains in proximal renal tubules. We present a case of a 59-year-old female with a 9-year established history of Sjögren’s syndrome (SS) who presented with progressive renal dysfunction. A comprehensive workup revealed a monoclonal IgA-kappa paraproteinemia and a renal biopsy confirmed LCPT. Her diagnosis of SS was re-confirmed with positive anti-SSA/Ro-52 antibodies and focal lymphocytic sialadenitis. The patient exhibited metabolic acidosis, hypophosphatemia, and hypokalemia, consistent with Fanconi syndrome. The long-standing nature of her autoimmune disease prior to the development of MGRS lends support to our unifying hypothesis: chronic antigenic stimulation from SS may drive clonal plasma cell expansion, leading to monoclonal gammopathy and subsequent renal light chain deposition. This case highlights the importance of considering MGRS in SS patients with worsening renal tubular dysfunction.