MON-492 - When Age Misleads: Autoimmune Addison'S Disease in Older Adults

Hyponatremia, hypotension, and altered mental status (AMS) are frequently encountered in older adults and often attributed to polypharmacy, dehydration, or chronic comorbid conditions. However, these nonspecific findings may also reflect adrenal insufficiency and warrant careful evaluation. Addison’s disease (AD), although uncommon in the elderly, should remain in the differential, particularly when gastrointestinal symptoms such as diarrhea, abdominal pain, or unexplained weight loss are present.

Autoimmune adrenalitis accounts for approximately 80 percent of adult cases of primary adrenal insufficiency. New diagnoses after age 60 are rare, representing fewer than 10 percent of cases, with an estimated incidence of 0.1 to 0.2 per 100,000 persons per year. While autoimmune AD is more commonly recognized in younger adults, it can present at any age. A high index of suspicion, combined with a thorough history and physical exam, is essential to avoid diagnostic delay and prevent life-threatening adrenal crisis.

Clinical

Case:
A 71-year-old woman with MGUS and coronary artery disease presented with weakness, nausea, diarrhea, poor oral intake, hypotension, and syncope. Labs revealed hyponatremia, hyperkalemia, hypercalcemia, non anion gap metabolic acidosis, acute kidney injury, and hypoglycemia. An evening cortisol in the emergency department was 1.2 µg/dL (N = 5 to 25). Stress-dose steroids were started but discontinued the following day due to her age, low pre-test probability for adrenal insufficiency, and absence of traditional risk factors.

Evaluation by endocrinology revealed marked hyperpigmentation. This, combined with the initial presentation and labs, prompted repeat morning cortisol of 0.4 µg/dL (N = 5 to 25) and ACTH of 446 pg/mL (N = 7 to 63), confirming primary adrenal insufficiency. Hydrocortisone and fludrocortisone were started. CT showed a stable 1.5 × 1.3 cm left adrenal nodule, and anti 21-hydroxylase antibodies were positive, confirming autoimmune AD.

Conclusion:
This case highlights the importance of maintaining diagnostic vigilance for conditions classically associated with younger populations, such as autoimmune AD, even in elderly patients. Nonspecific presentations, including hyponatremia, hypotension, gastrointestinal symptoms, and AMS, may obscure the underlying diagnosis and contribute to delays in care. In this patient, careful bedside assessment and recognition of hyperpigmentation prompted targeted endocrine evaluation, leading to timely diagnosis. Primary adrenal insufficiency can present subtly yet progress rapidly without intervention. Early recognition and prompt initiation of glucocorticoid and mineralocorticoid replacement are lifesaving. This case underscores the enduring value of meticulous clinical examination and reinforces the role of bedside skills in guiding diagnostic reasoning and patient outcomes.

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