Pernicious anemia (PA) is an autoimmune atrophic gastritis, predominantly of the fundus, and is responsible for a deficiency in vitamin B12 (cobalamin) due to its malabsorption. Its prevalence is 0.1% in the general population and 1.9% in subjects over the age of 60 years. Pernicious anemia represents 20%-50% of the causes of vitamin B12 deficiency in adults. Given its polymorphism and broad spectrum of clinical manifestations, pernicious anemia is a great pretender. Its diagnosis must therefore be evoked and considered in the presence of neurological and hematological manifestations of undetermined origin. Biologically, it is characterized by the presence of anti-intrinsic factor (IF) antibodies. It binds to B12 to form a complex that is necessary for the absorption of the B12 in the small intestine. 40-60% of PA patients test positive for IF. Parietal Cells Antibodies (PCA) attack parietal cells. The cells normally produce the acids that release the B12 from food, and the IF that binds to it. The majority of PA patients will have PCAs. But it is not as specific as IF.