A New Diagnosis of Autoimmune Addison's Disease in an 80-Year-Old Female.

Hyponatremia is a common cause of hospitalization in older adults. Addison's disease (AD), an uncommon cause of hyponatremia, is primary adrenal insufficiency (AI) caused by autoimmune adrenalitis, infections, adrenal hemorrhage, or infiltration. Autoimmune adrenalitis is an uncommon cause of AD after age 60 years. We report the case of an 80-year-old female with steroid-controlled asthma, who was diagnosed with primary AI after presenting with weakness, nausea, vomiting, and hyponatremia two weeks after a urinary tract infection (UTI). Further testing revealed a positive 21 hydroxylase antibody confirming autoimmune AD. The patient has done well on hydrocortisone and fludrocortisone daily with occasional need for stress dosing during infections. AD should be considered as a cause of hyponatremia in hospitalized elderly patients. Non-specificity of symptoms of AD makes the diagnosis difficult in this age group, often causing delays in the appropriate management. Our patient's autoimmune AD was masked by intermittent steroid use over the years. During the COVID-19 pandemic, masking and social distancing decreased her steroid needs and unmasked AD after the UTI. We highlight the importance of considering AD as a cause of hyponatremia and autoimmune AD as a cause of AI even in the elderly.