Intramuscular Cyanocobalamin Treatment in Patients with Corpus Atrophic Gastritis and Vitamin B12 Deficiency: Efficacy and Predictors of Increased Requirement—A Monocentric Longitudinal Real-Life Cohort Study

Background and Objectives: Corpus atrophic gastritis (CAG) is associated with vitamin B12 deficiency due to impaired gastric acid and intrinsic factor secretion. Untreated vitamin B12 deficiency can lead to pernicious anemia, severe neurological consequences, and acute cardiocerebral-vascular events. Timely vitamin B12 supplementation is relevant; however, the dosage of intramuscular (IM) vitamin B12 supplementation has not been standardized to date. The objective was to assess the efficacy of a 1st and 2nd treatment schedule of IM-cyanocobalamin treatment in CAG patients with vitamin B12 deficiency at long-term follow-up and to identify the predictors of increased cyanocobalamin requirement. Methods: This monocentric real-life cohort study included 213 CAG patients with vitamin B12 deficiency. Inclusion criteria were adult age, histological diagnosis of CAG with vitamin B12 deficiency (