Esthesioneuroblastoma as a Cause of Syndrome of Inappropriate Antidiuretic Hormone

Esthesioneuroblastoma (ENB) is a rare neuroendocrine malignancy of the olfactory epithelium that lines the superior nasal cavity that may uncommonly present with syndrome of inappropriate antidiuretic hormone (SIADH). We present the case of a 37-year-old woman with history of primary hypothyroidism and systemic lupus erythematosus (SLE) presenting with SIADH 2.5 years prior to diagnosis of a left nasal cavity ENB (Kadish's stage B, Hyams' grade 1) who experienced resolution of her hyponatremia over 24 hours following transnasal endoscopic resection of the tumor, with negative margins. Her sodium levels were below 120 mEq/L at initial presentation, and diagnosis of SIADH was obfuscated by concomitant discovery of a pituitary microadenoma, primary hypothyroidism, and adrenal insufficiency due to long standing corticosteroid use for SLE. Her sodium levels were maintained in the range of 126 to 130 mEq/L through fluid restriction and salt tablets. The ENB was later discovered when patient developed epistaxis with magnetic resonance imaging (MRI) showing interval progression of disease (Figs. 1–2). Our patient experienced resolution of her hyponatremia over 24 hours following transnasal endoscopic resection of the tumor, with negative margins. Through a review of the literature, we were able to identify 45 previously reported cases in the world literature starting from 1987. Of these cases, the average reported age was 37 years (n = 38), with a slight female predominance (23/40; 58%). In the 39 cases with sufficient detail, ENB and SIADH were diagnosed within the same time frame in 16 (41%), and SIADH was diagnosed prior to ENB in 19 (49%). SIADH diagnosis preceded ENB by up to 16 years with a median preceding time of 3.5 years in the 18 cases reporting specific timeline information. In the 38 cases reporting on SIADH resolution, 35 (92%) had resolution following definitive ENB treatment, which was surgery in all but one case, two additional cases experienced delayed resolution following multiple treatment modalities, and one case had no resolution of SIADH, with the patient eventually passing due to disease. Overall, ENB is a treatable cause of SIADH with presentation of SIADH preceding ENB diagnosis in over half of the cases reported in the literature. Though uncommon, SIADH of unknown origin should always introduce suspicion for an occult malignancy such as ENB. In patients with ENB with associated SIADH, repeat sodium levels may provide an additional screening method for recurrence.

Fig. 1 Axial MRI during initial SIADH work-up. MRI, magnetic resonance imaging; SIADH, syndrome of inappropriate antidiuretic hormone.

Fig. 2 Axial MRI at time of ENB diagnosis. ENB, esthesioneuroblastoma; MRI, magnetic resonance imaging.

No conflict of interest has been declared by the author(s).

Publication History

Article published online:
12 February 2021