Autoimmune Polyglandular Syndrome Type 3 and Overlapping Autoimmune Endocrinopathies: A Case Report.

Autoimmune polyglandular syndrome type 3 (APS type 3) is defined by the coexistence of autoimmune thyroid disease with other autoimmune disorders, excluding adrenal insufficiency. It is a common but often under-recognized entity, particularly in young women with multiple autoimmune conditions. We report the case of a 27-year-old woman with a longstanding history of type 1 diabetes mellitus (T1DM) who presented with multiple episodes of diabetic ketoacidosis to the emergency department. She presented with fatigue and had poor glycemic control (HbA1c 11.3%). She was further diagnosed in the ward with refractory autoimmune hypothyroidism, pernicious anemia, celiac disease with poor dietary adherence, and proliferative diabetic retinopathy requiring retinal intervention. Physical examinations, blood workup, and radiological investigations revealed no signs of adrenal insufficiency or pituitary adenoma. The combination of autoimmune thyroid disease, T1DM, pernicious anemia, celiac disease, and systemic autoimmunity, in the absence of adrenal involvement, is consistent with a diagnosis of APS type 3 with overlapping subtypes. This case illustrates the clinical complexity and diagnostic challenges of APS type 3. Early identification and multidisciplinary management of coexisting autoimmune disorders are essential for improving long-term outcomes and reducing complications. Attention to dietary adherence, appropriate thyroid hormone dosing, and ongoing screening for evolving autoimmune involvement are critical elements in the care of such patients.