Introduction: Autoimmune polyglandular syndromes (APS) are rare diseases defined by the coexistence of at least two autoimmune endocrine diseases. Objective: To describe a case of type III polyglandular syndrome in a young patient. Case report: Female, 37 years old, with hypothyroidism, presented with a weight loss of 9 kg, daily vomiting, asthenia, fatigue, and postprandial fullness for 3 months. He also reported arthritis in his wrists, shoulders, and hips. In laboratory tests, macrocytic and hyperchromic anemia associated with leukopenia, as well as hypovitaminosis B12, was observed. Pernicious anemia was investigated as the cause of this deficiency. Upper digestive endoscopy showed moderate gastritis – histopathological with gastric atrophy, positive anti-intrinsic factor antibody. Due to inflammatory arthralgia, ANA was requested, with an associated positive anti-dsDNA result of 1:80. In the EULAR/2019 diagnostic criteria for Systemic Lupus Erythematosus (SLE), she presented 14 points, thus she was diagnosed with SLE, and hydroxychloroquine (HXC) was started. Conclusion: SPA is rare, mainly in association with non-glandular autoimmunity, following an early diagnosis.