RESUMEN
Autoimmune polyendocrine syndrome (APS) type 3B is characterized by presence of autoimmune thyroid disease, chronic atrophic gastritis and pernicious anemia. In this report, we present a rare case of APS type 3B with neuropathy by thiamine deficiency. A 65-year-old man had a history with hypothyroidism, gastritis, gastrectomy for gastric cancer and subacute combined degeneration of the spinal cord. Patient developed polyneuropathy with not mecobalamin but thiamine deficiency. Serum anti-thyroglobin (TG), anti-thyroid peroxidase (TPO), and anti-gastric parietal cell antibodies were positive. He was treated with thiamine supplementation and improved muscle weakness, sensory impairment and gait disturbance. Classically, it is reported gastric cancer related to hypothyroidism. Additionally, thiamine deficiency can be caused by gastrectomy. Here, his thiamine deficiency was related to APS type 3B, leading to polyneuropathy.