SUN-420 Twin Discordance In Primary Adrenal Insufficiency: Hyperpigmentation As The First Overlooked Symptom

Abstract Disclosure: M. Fatima: None. C. Taylor: None. T. Nawaz: None. Background: Generalized hyperpigmentation is a known early symptom of adrenal insufficiency. Other symptoms include nausea (90%), fatigue (70%), and hyperkalemia (50%), which can culminate in a life-threatening adrenal crisis. Therefore, early and prompt recognition of Addison’s disease is important when evaluating patients with mucocutaneous pigmentation. This is clearly illustrated by the following case of a patient who presented with 3-4 months of isolated generalized hyperpigmentation, which was in stark contrast to her identical twin. Unfortunately, this symptom did not prompt further investigation, and she later presented to the emergency department in adrenal crisis. Case Presentation: An 18-year-old previously healthy female presented to the emergency department with a one-week history of worsening nausea, vomiting, dizziness, and fatigue, following 3-4 months of generalized skin darkening that had been unfortunately ignored until her acute decompensation. On arrival, she was clinically dehydrated, with a blood pressure of 85/55 mmHg and hyponatremia. Laboratory evaluation revealed a morning cortisol level of 1.3 μg/dL, and an ACTH stimulation test showed no appreciable rise in cortisol, confirming primary adrenal insufficiency. Imaging of the abdomen and pelvis was unremarkable aside from mild mesenteric adenitis. She was treated with IV hydrocortisone (Solu-Cortef) 10 mg twice daily, resulting in rapid symptom improvement and correction of hyponatremia. She was discharged on oral hydrocortisone and fludrocortisone with a referral for endocrinology follow-up. She was advised on adrenal crisis precautions and prescribed emergency injectable steroids. Family history was negative for autoimmune medical conditions. The patient tested negative for AIRE mutations but was advised to undergo further genetic testing, both to determine her own risk profile and to assess potential implications for her sibling. Conclusion: In summary, mucocutaneous hyperpigmentation may represent the first sign of primary adrenal insufficiency. The stark contrast with the patient’s identical twin highlighted this symptom’s significance, yet it still did not prompt additional investigation in the absence of other symptoms. Although the twin sibling is currently asymptomatic, genetic testing and regular evaluations should be conducted to ensure early diagnosis and timely intervention. Presentation: Sunday, July 13, 2025