Severe Hyponatremia Presenting with Mild Symptoms and Multifactorial Etiology

Hyponatremia is a common electrolyte disturbance; however, serum sodium level of 99 mEq/L without severe symptoms or known duration is rare and noteworthy. We report a case of an 87-year-old female who presented with fatigue, decreased appetite, and mild emesis for the past 2 days in which blood work revealed a serum sodium level 99 mEq/L. The etiology of hyponatremia in an elderly patient may be complex due to higher likelihood of co-morbid medical conditions. Additionally, syndrome of inappropriate antidiuretic hormone (SIADH) can pose a diagnostic challenge as fewer than 50% of patients have typical lab results that confirm the diagnosis (1).