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Abstract: FR-PO666

Symptomatic Hyponatremia: SIADH or NSIAD): Diagnostic Challenge, Surprise Diagnosis, and Successful Management with Tolvaptan for 6 Years

Session Information

Category: Fluid and Electrolytes

  • 902 Fluid and Electrolytes: Clinical

Authors

  • Chadha, Vimal, Children's Mercy Hospital, Kansas City, Missouri, United States
  • Beahm, D. David, University of Kansas, Kanasa City, Kansas, United States
  • Alon, Uri S., The Children's Mercy Hospital and Cklinics, Kansas City, Missouri, United States
Introduction

Syndrome of inappropriate antidiuretic hormone secretion (SIADH) is the most common cause of euvolemic hyponatremia. In the absence of any identifiable cause after extensive investigations, and especially in the presence of low or undetectable serum ADH level, diagnoses such as nephrogenic syndrome of inappropriate antidiuresis (NSIAD) caused by gain-of-function mutations in the V2 vasopressin receptor (V2R) have to be entertained. Chronic management of symptomatic hyponatremia can also be a challenge.

Case Description

A 17 year old previously healthy girl presented with dizziness, and short-term memory loss. Blood tests revealed serum sodium 128 mEq/L. Clinical picture was suggestive of SIADH (euvolemic state, low serum osmolality, increased urinary osmolality, and increased urinary sodium level) but extensive investigations/imaging studies failed to delineate any underlying cause for SIADH. Review of old medical records revealed normal serum sodium (142 mEq/L) over a decade ago. She was managed as possible SIADH, with water restriction that resulted in modest improvement in her serum sodium level. A month later her symptoms recurred with recurrence of hyponatremia. Serum ADH levels returned undetectable on both occasions and were confirmed to be low 3rd time from two different labs. Later, her serum sodium acutely dropped to 119 mEq/L when she drank water prior to a renal ultrasound. She was suspected having NSIAD but DNA sequencing of V2R gene did not show any mutation. She was managed with combination of moderate fluid restriction and daily Tolvaptan. Five years later, she had seizures with severe hyponatremia (109 mEq/L) after taking SSRI for depression. 1½ year later she had another episode of unexplained hyponatremia (118 mEq/L), and a head MRI was repeated for headache after correction of hyponatremia which revealed a small enhancing mass in the right osteomeatal infundibulum. The mass turned out to be small blue cell tumor esthesioneuroblastoma, a relatively rare nasal tumor that is rarely associated with SIADH. She underwent complete tumor resection with clear margins, and now has normal serum sodium without any fluid restriction or medications.

Discussion

Patients with chronic unexplained hyponatremia should be followed very closely and reevaluated periodically with high index of suspicion for unusual tumors.