Autoimmune polyglandular syndrome (APS) is an autoimmune disease with a variety of clinical manifestations that is characterized by a spectrum of association between two or more organ-specific endocrinopathies and non-endocrine autoimmune diseases. APS type 2 (APS-2) is characterized by the coexistence of Addison’s disease with autoimmune thyroid disease and type 1 diabetes mellitus (T1DM). Alopecia universalis is rarely associated with these autoimmune disorders. Here, we report a case of a 39- year-old diabetic man with a known history of hyperthyroidism. Two years prior, the patient experienced sudden loss of hair, eyebrows, eyelashes, beard, hirci, and pubes, leading to a diagnosis of alopecia universalis, accompanied by vitiligo and rheumatoid arthritis. He was ultimately diagnosed with APS-2. The patient was prescribed an anti-thyroid drug and insulin. During follow-up, the patient’s thyroid function test was normal and his blood glucose level was relatively stable. This case could easily be misdiagnosed as hyperthyroidism co-existent with T1DM. This provides an important reference standard for understanding APS.