October - December 2013, Volume 9, Issue 4

Diaconu CC, Arsene D, Paraschiv B, Balaceanu A, Bartos D

Hyponatremic Encephalopathy as the Initial Sign of Neuroendocrine Small Cell Carcinoma: Case Report

Acta Endo (Buc) 2013, 9 (4): 637-643
doi: 10.4183/aeb.2013.637

Background. Small-cell lung carcinoma is a neuroendocrine tumor that exhibits aggressive behavior, rapid growth, early spread to distant sites and frequent association with paraneoplastic syndromes, the most frequent being the syndrome of inappropriate secretion of antidiuretic hormone (SIADH). Case report. We present the case of a 66 year-old woman who presented to the Emergency Department for a syncope preceded by vomiting. She had onemonth history of progressive confusion, disorientation, drowsiness, and generalized malaise. At presentation, the biochemical profile showed normal hemogram values, severe hyponatremia (seric sodium level 120 mg/dL), low plasma osmolality (<275 mOsm/ kg). The blood tests for kidney, thyroid and adrenal functions were in normal limits. There was no evidence of congestive heart failure or nephrotic syndrome. A diagnosis of SIADH was made. Because of a high suspicion for lung cancer, chest computed tomography (CT) was done, together with neck, abdominal and pelvic CT scan, all showing normal data, excepting necrotic lymph nodes in the lower right carotid space and right paratracheal. Right laterocervical lymph node biopsy was done. The histopathological and immunohistochemical result showed lymph node metastasis of a neuroendocrine small cell carcinoma, most probably with broncho-pulmonary origin. Conclusion. The case is interesting due to long term absence of any respiratory symptom, absence of identification of pulmonary tumor, despite repeated CT scans, the only clinical manifestations being related to SIADH. Also, it emphasizes the importance of early recognition of SIADH, which may be the only initial manifestation of a neuroendocrine small cell carcinoma.

Keywords: hyponatremia, SIADH, neuroendocrine carcinoma

Correspondence: Camelia Cristina Diaconu MD, “Carol Davila” University of Medicine and Pharmacy, Internal Medicine Clinic, Clinical Emergency Hospital of Bucharest, 8 Calea Floreasca, Sector 1, Bucharest, 014461, Romania, E-mail: camiluciemi@yahoo.com