Abstract: FR-PO0607
Dilution Confusion: Unmasking Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH) in Multiple Myeloma
Session Information
- Fluid, Electrolyte, and Acid-Base Disorders: Clinical - 2
November 07, 2025 | Location: Exhibit Hall, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Fluid, Electrolytes, and Acid-Base Disorders
- 1102 Fluid, Electrolyte, and Acid-Base Disorders: Clinical
Authors
- Iftikhar, Nimra, The University of New Mexico School of Medicine, Albuquerque, New Mexico, United States
- Quinones Vargas, Irmaris Raquel, The University of New Mexico School of Medicine, Albuquerque, New Mexico, United States
- Soleimani, Manoocher, The University of New Mexico School of Medicine, Albuquerque, New Mexico, United States
Introduction
Hyponatremia is a well-documented electrolyte abnormality in individuals with multiple myeloma. Both “True” and “Pseudo” hyponatremia have been described in multiple myeloma. True Hyponatremia has been observed due to increased cationic circulating immunoglobulins in multiple myeloma. SIADH as the etiology of hyponatremia in multiple myeloma is a very rare occurrence. Here we report an individual with Multiple Myeloma who was admitted with significant hyponatremia.
Case Description
An 88-year-old patient with a known diagnosis of multiple myeloma, on Thalidomide, presented with shortness of breath and generalized weakness. On arrival, the patient was found to be hyponatremic with a serum sodium of 120 and serum potassium of 4.0 mEq/l. The BUN was 18 mg/dl, and serum creatinine was 0.65 mg/dl. The blood sugar was 152 mg/dl. Circulating immunoglobulins were significantly elevated. The workup for hyponatremia revealed a serum osmolality of 258 and a urine osmolality of 440 mOsm/lit. The urinary electrolytes were (in mEq/l) sodium 133, potassium 29, and chloride 122. The serum HCO3- concentration on admission was 18 mEq/l. The blood and urine chemistries were consistent with the diagnosis of SIADH. The secondary causes of SIADH, such as hypothyroidism, adrenal insufficiency, and medications, were excluded. There was no evidence of Fanconi Syndrome or hypercalcemia.
Discussion
To avoid the impact of fluid restriction in provoking acute kidney injury in multiple myeloma, the patient was started on urea at 15 gm/day and sodium tablets of 3 gm, TID. The serum Na concentration improved to 128 mEq/l after 6 days. While the exact association between multiple myeloma and SIADH remains speculative, one report suggested that enhanced IL-6 production by myeloma cells may stimulate AVP secretion. Establishing the diagnosis of SIADH should guide the options for the treatment of hyponatremia in multiple myeloma.