Coexistence of Addison's Disease and Pernicious Anemia: Is the New Classification of Autoimmune Polyglandular Syndrome Appropriate?

A case of autoimmune polyglandular syndrome (APS) is presented. A 45-year-old man was admitted due to fatigue, malaise and inappetence. He had a history of primary hypothyroidism and was on levothyroxine substitution therapy. One year before, he was diagnosed with normocytic anemia and vitamin B12 deficiency, which was treated with vitamin B12 substitution therapy. Physical examination revealed hypotension and marked hyperpigmentation. Laboratory testing showed hyponatremia, hyperkaliemia and severe normocytic anemia. Endocrinological evaluation disclosed low morning cortisol and increased adrenocorticotropic hormone levels. Hence, the diagnosis of Addison's disease was established. Additional laboratory workup showed positive parietal cell antibodies. However, his vitamin B12 levels were increased due to vitamin B12 supplementation therapy, which was initiated earlier. Gastroscopy and histopathology of gastric mucosa confirmed atrophic gastritis. Based on prior low serum vitamin B12 levels, positive parietal cell antibodies and atrophic gastritis, the patient was diagnosed with pernicious anemia. Hydrocortisone supplementation therapy was administered and titrated according to urinary-free cortisol levels. Electrolyte disbalance and red blood cell count were normalized. This case report demonstrates rather unique features of pernicious anemia in a patient with Addison's disease. It also highlights the link between type II and type III APS. Not only do they share the same etiological factors, but also overlap in pathophysiological and clinical characteristics. This case report favors older classification of APS, which consolidates all endocrine and other organ-specific autoimmune diseases into one category. This is important since it might help avoid pitfalls in the diagnosis and treatment of patients with APS.