Electrolyte Blood Press.  2017 Dec;15(2):42-46. 10.5049/EBP.2017.15.2.42.

Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH) Associated with Mediastinal Schwannoma

• Song SH
• Sim GA
• Baek SH
• Seo JW
• Shim JW
• Koo JR

• KMID: 2401152
• DOI: http://doi.org/10.5049/EBP.2017.15.2.42

Abstract

Syndrome of inappropriate antidiuretic hormone secretion (SIADH) is the most common cause of euvolemic hypo-osmotic hyponatremia. There are several etiologies of SIADH including neuroendocrine tumor, pulmonary disease, infection, trauma, and medications. Here, we report a case of SIADH associated with a schwannoma involving the mediastinum in a 75-year-old woman who presented with nausea, vomiting, and general weakness. Laboratory testing showed hypo-osmolar hyponatremia, with a serum sodium level of 102mmol/L, serum osmolality of 221mOsm/kg, urine osmolality of 382mOsm/kg, urine sodium of 55 mmol/L, and plasma antidiuretic hormone (ADH) of 4.40 pg/mL. Chest computed tomography identified a 1.5-cm-sized solid enhancing nodule in the right lower paratracheal area. A biopsy specimen was obtained by video-assisted thoracoscopic surgery, which was diagnosed on pathology as a schwannoma. The hyponatremia was completely resolved after schwannoma resection and plasma ADH level decreased from 4.40 pg/mL to 0.86 pg/mL. This case highlights the importance of suspecting and identifying the underlying cause of SIADH when faced with refractory or recurrent hyponatremia, and that on possibility is mediastinal schwannoma

Keyword

Hyponatremia; Syndrome of Inappropriate ADH (SIADH) Secretion; Mediastinal schwannoma

MeSH Terms

Aged
Biopsy
Female
Humans
Hyponatremia
Inappropriate ADH Syndrome
Lung Diseases
Mediastinum
Nausea
Neurilemmoma*
Neuroendocrine Tumors
Osmolar Concentration
Pathology
Plasma
Sodium
Thoracic Surgery, Video-Assisted
Thorax
Vomiting
Sodium

Figure

• 

  Fig. 1 Enhanced chest computed tomography. A hyper-attenuated solid enhancing nodule can be seen in the right lower paratracheal area (arrow)

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  Fig. 2 Microscopic images of the mediastinal schwannoma. (A) Markedly increased cellularity and fascicles of spindle cells in a loose stroma (hematoxylin and eosin staining, 40×). (B) Immunohistochemical analysis showing diffuse strong positivity for S-100 (40×).

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  Fig. 3 Serum sodium level of the patient during hospitalization. The sodium level recovered during infusion of hypertonic saline, but decreased after discontinuation of hypertonic saline. The patient's serum sodium was completely recovered after schwannoma excision by VATS. HD, hospital day; POD, post-operative day; VATS, video-assisted thoracoscopic surgery.

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