A patient diagnosed with new-onset type 1 diabetes and Addison's disease at initial presentation.

Summary: A previously healthy 17-year-old female presented to the emergency department with complaints of vomiting, shortness of breath, and tachycardia. She was found to have an elevated blood glucose and was admitted for presumed new onset type 1 diabetes mellitus (T1DM). During the admission, she was noted to have frequent episodes of hypoglycemia despite conservative insulin dosing and high urine output with glucosuria, which seemed out of proportion to her glucose levels and fluid status. She also had persistent hyponatremia despite normalization of blood glucose. Further work-up was initiated to investigate alternative or additional diagnoses to explain these atypical findings. Adrenocorticotropic hormone (ACTH) level was elevated, consistent with the diagnosis of Addison's disease, which led to the subsequent diagnosis of autoimmune polyglandular syndrome type II (APS-2). This is one of the first reports in the literature of concurrent diagnosis of T1DM and Addison's disease at initial presentation and demonstrates the importance of not anchoring to one diagnosis. Learning points: This case shows the importance of considering multiple diagnoses and investigating atypical signs and symptoms. This case highlights the importance of a thorough history including review of systems. Hyponatremia and recurrent hypoglycemia in a person with type 1 diabetes should raise suspicion for adrenal insufficiency. This case makes us consider the screening for Addison's disease in a person with new onset type 1 diabetes in addition to autoimmune thyroid disease and celiac disease. People with an autoimmune disease should be monitored for other autoimmune diseases in the future.