Abstract: SA-PO0217
Investigation of Hyponatremia Leading to the Diagnosis of Sjögren Syndrome and Waldenström Macroglobulinemia
Session Information
- Onconephrology: MGRS, HSCT, Electrolytes, RCC, and More
November 08, 2025 | Location: Exhibit Hall, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Onconephrology
- 1700 Onconephrology
Authors
- Saldanha Neves Horta Lima, Carolina, Mass General Brigham Inc, Boston, Massachusetts, United States
- Martins, Cilomar, Mass General Brigham Inc, Boston, Massachusetts, United States
- William, Jeffrey H., Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States
Introduction
We describe a case of chronic pseudo-hyponatremia due to hyperproteinemia from monoclonal gammopathy alongside acute kidney injury with sub-nephrotic proteinuria, found to have a kidney biopsy pattern consistent with Sjogren’s syndrome.
Case Description
A 58-year-old female presented with persistent hyponatremia and rising creatinine. Sodium had ranged from 131–133 mmol/L over four years, with creatinine increasing from 1.08 to 1.60 mg/dL. Serum osmolality was 300 mOsm/kg, urine osmolality 385 mOsm/kg, and glucose 98 mg/dL—suggestive of pseudo-hyponatremia. This was confirmed by a normal sodium on direct measurement. Triglycerides were normal.
Urinalysis was unremarkable. Serum protein electrophoresis revealed a 2.3 g/dL spike in the gamma region. Free kappa light chains were 220.8 mg/L with a kappa/lambda ratio of 6.1. Urine protein/creatinine ratio was 252 mg/g with a globulin M-spike of 2.9 mg/dL. Immunofixation was positive for free kappa and faint free lambda light chains.
Bone marrow biopsy showed <10% infiltration by lymphoplasmacytic lymphoma with a MYD88 mutation consistent with Waldenström macroglobulinemia (WM). Kidney biopsy demonstrated chronic-active tubulointerstitial nephritis without lymphoplasmacytic infiltration, with a pattern suggesting Sjogren’s syndrome, then confirmed by positive SS-A and SS-B antibodies. On further questioning, she endorsed longstanding xerophthalmia.
She was treated with a course of prednisone, leading to improvement in renal function (creatinine to 1.15 mg/dL), though proteinuria remained stable. Hematology deemed her WM low risk, not requiring therapy.
Discussion
This case highlights the importance of thoroughly investigating chronic hyponatremia, which led to the diagnosis of an underlying lymphoproliferative disorder. It also emphasizes the need to maintain a broad differential for tubulointerstitial nephritis
Primary Sjogren’s syndrome is marked by B-cell hyperactivity, often with polyclonal hypergammaglobulinemia, elevated free light chains, and rheumatoid factor positivity. pSS increases the risk for B-cell lymphomas, with disease activity as a risk factor. In this case, pseudo-hyponatremia due to light chains was the initial clue that revealed both WM and pSS-related renal involvement—illustrating an uncommon but informative diagnostis.