Abstract
INTRODUCTION: Hyponatremia is a common finding in hospitalized patients, especially the elderly. Symptoms of hyponatremia can vary depending on the concentration of sodium in serum as well as the dynamics of its escalation. Hyponatremia can have many etiologies, including medication, vomiting, or diarrhea, and central nervous system disorders, including tumors, trauma, and infections. CASE REPORT: In this case, we present a 74-year-old patient who was admitted to the Department of Internal Medicine with symptomatic, acute, and severe hyponatremia in the course of the syndrome of inappropriate antidiuretic hormone secretion due to varicella zoster virus meningoencephalitis. Clinical improvement and normalization of natremia occurred after the initiation of causal treatment. CONCLUSION: Given the complexity of the potential causes of hyponatremia and the variety of treatments available, it is essential to thoroughly consider the possible reasons for electrolyte abnormalities, including uncommon ones such as central nervous system infections.