SUN-076 Neurological and Endocrine Crossroads: A Rare Case of HHV-6 Encephalitis Inducing Central Diabetes Insipidus

Abstract Disclosure: V. Shah: None. P. Patel: None. G. Singh: None. C. Bheeman: None. R. Sharma: None. Background: Human herpesvirus 6 (HHV-6) is a neurotropic virus known to cause encephalitis, particularly in immunocompromised individuals. HHV6 commonly infects children, causing exanthema subitum. As a result, most adults have antibodies, and HHV6 encephalitis is rare in immunocompetent adults. However, its association with central diabetes insipidus (CDI) is rare.Case Presentation: We report a case of a 33-year-old female with a history of Sjogren’s syndrome who presented with altered mental status and was diagnosed with HHV-6 encephalitis via lumbar puncture that was treated with ganciclovir. Her hospital course was complicated by metabolic derangements, including severe hypernatremia (plasma sodium: 165-170 mEq/L), elevated serum osmolarity 356 mOsml/kg, copeptin level 19.4 pmol/L, polydipsia, and polyuria. Brain MRI revealed reduced diffusivity and edema involving the amygdala and hippocampus bilaterally. Given her clinical presentation and imaging findings, she was suspected to have CDI and treated with desmopressin (DDAVP), leading to symptomatic improvement. Conclusion: This case highlights a rare presentation of HHV-6 encephalitis causing CDI, suggesting potential hypothalamic involvement. Clinicians should consider CDI in encephalitis patients with severe hypernatremia and polyuria, as early recognition and treatment are essential for preventing complications. Presentation: Sunday, July 13, 2025