Autoimmune Polyglandular Syndrome Type 3: A Case Report.

Autoimmune polyglandular syndromes (APS) are characterized by associations of two or more autoimmune diseases (AID). APS type 3 is characterized by the presence of autoimmune thyroid disease associated with other AID, excluding adrenal gland involvement. Here we report a case of a 64-year-old male, with history of type 1 diabetes mellitus (T1DM), diagnosed at the age of 32, who was referred to a Diabetes consultation in 2014 due to poor metabolic control. An optimized intensive insulin regimen with basal insulin glargine and aspart insulin at all meals was implemented. During the investigation, he tested positive for anti-glutamic acid decarboxylase (GAD) 65, anti-islet cell (ICA) and anti-insulin antibodies. In 2019, the patient exhibited achromic spots on the chin, bilateral cervical region, and right hip, and was referred to a dermatology consultation, where he was diagnosed with vitiligo. In a follow-up appointment in 2020, a blood test showed macrocytic anemia with vitamin B12 deficiency. An upper gastrointestinal endoscopy revealed chronic pangastritis. Positive anti-gastric parietal cell antibodies and negative anti-intrinsic factor antibodies led to a diagnosis of chronic autoimmune gastritis, and the patient started monthly injectable vitamin B12 supplementation. Thyroid antibodies were tested to screen for other AID, revealing positive anti-thyroid peroxidase antibodies. The patient had slightly elevated thyrotropin (thyroid-stimulating hormone (TSH)) with normal free thyroxine (FT4), indicating subclinical hypothyroidism that did not require supplementation, and remained under surveillance. Adrenocorticotropic hormone (ACTH) and cortisol levels were normal, ruling out adrenal involvement. This case demonstrates a type 1 diabetic patient additionally diagnosed with vitiligo, chronic autoimmune gastritis, and chronic autoimmune thyroiditis. Excluding adrenal gland involvement, this constitutes a diagnosis of APS3. Type 1 diabetes mellitus alone poses an increased risk of developing other AID, which can be diagnosed in pre-symptomatic stages through the monitoring of specific autoantibodies, highlighting the importance for clinicians to remain vigilant even in the absence of specific symptoms.