Neuroinflammation-Induced SIADH in West Nile Virus Infection: An Uncommon Neurological and Endocrine Manifestation

BACKGROUND West Nile virus (WNV) is a vector-borne flavivirus that is typically transmitted by Aedes and Anopheles mosquitos. WNV infection typically presents with symptoms consistent with viral meningitis, which include fever, headache, and meningeal signs. WNV infections are typically self-resolving, with symptoms lasting 3-10 days. Although uncommon, patients with WNV infection can be afflicted with hyponatremia, although the etiology is unclear. Because of encephalitis, neuroinflammation may be involved in the deterioration of adrenal signaling, leading to salt wasting. CASE REPORT We present the case of a 75-year-old man who presented with headache, neck pain, photophobia, and viral illness symptoms. He was found to be profoundly hyponatremic, concerning for SIADH. He had a sodium drop to 117 mmol/L, leading to further lethargy and confusion. He received 3% saline, fluid restriction, and salt tablets, and more common causes of SIADH were ruled out. MRI revealed the absence of the posterior pituitary bright spot. He was subsequently found to have positive WNV titers and improved with continued supportive treatment. CONCLUSIONS WNV presents a unique challenge to providers due to its difficult diagnosis and association with hyponatremia. There is no clear role for specific medical treatment such as corticosteroids vs IV immunoglobulins. Supportive care is recommended for those testing positive for WNV. Clinicians should consider the possibility of viral infections, such as WNV, in patients living in endemic areas who present with unexplained hyponatremia, cognitive symptoms, and relevant history.