Syndrome of Inappropriate Antidiuretic Hormone Secretion - A Rare Initial Presentation of Lyme Neuroborreliosis (P9-10.005)

Abstract

<h3>Objective:</h3> NA <h3>Background:</h3> Lyme disease is the most common vector-borne disease in the northern hemisphere. Lyme neuroborreliosis can be diagnostically challenging due to its diverse manifestations. Early disseminated stage may exhibit a neurological spectrum that includes cranial neuropathy, radiculoneuritis, and lymphocytic meningitis. Cranial neuropathy is a typical initial manifestation. We present a case of Lyme neuroborreliosis with SIADH and thoracic radiculopathy as a first presentation followed by cranial neuropathy. <h3>Design/Methods:</h3> NA <h3>Results:</h3> <h3>Case Report:</h3> A 66-year old man with past medical history of laryngeal cancer status post radiation presented with band-like pain across the right chest and abdomen in July 2021. Lab workup revealed hypotonic hyponatremia (119 mmol/L). It was thought to be multifactorial due to SIADH and the use of hydrochlorothiazide. It was managed with fluid restriction. The patient was also treated for a presumed diagnosis of varicella without rash. Five days later, he returned with a right facial droop and right vision changes. Examination showed peripheral right facial weakness. A repeat lab workup revealed hypotonic hyponatremia (123mmol/L). He was diagnosed with SIADH. MRI brain and orbit were consistent with right cranial nerve VII enhancement. The Lyme antibody panel was positive. He was retrospectively diagnosed with thoracic radiculoneuritis in the setting of Lyme disease. Ultimately, he was treated with doxycycline and discharged home. <h3>Conclusions:</h3> Lyme neuroborreliosis rarely presents with SIADH and thoracic radiculoneuritis as the first manifestation. This case further adds to the growing evidence of the association of Lyme neuroborreliosis with SIADH. The mechanism of this phenomenon remains unclear; likely related to the inflammation cascade induced by CNS infection. Prompt recognition is critical for timely diagnosis and treatment. <b>Disclosure:</b> Dr. Singh has nothing to disclose. Dr. Zahra has nothing to disclose. Dr. Chu has nothing to disclose. Dr. Kokash has nothing to disclose. Dr. Varrato has nothing to disclose.