[Pathophysiology of hypervitaminosis B12: from origin to clinical event. Scoping review].

The role that hypervitaminosis B12 may play in the clinical course of various diseases is controversial, in addition to being an overlooked laboratory finding. The objective of this review was to map the literature regarding the pathophysiological mechanisms that explain the increased serum levels of vitamin B12 (vB12) in some adult diseases. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses-Scoping Review Extension (PRISMA-ScR) checklist guided this scoping review. The search was performed in 2 electronic databases (PubMed and Google Scholar), in Spanish and English, for the years between 2000 and 2024. Twenty studies out of 568 found and screened were included. The main pathophysiological mechanisms that explained the hypervitaminosis B12 were 3: (1) oral or parenteral supplementation of vB12, which can induce the formation of autoantibodies anti-transcobalamin II; (2) serum increase of transcobalamins I, II and III by overproduction or reduction in their clearance; and (3) functional deficiency of the metabolism of transcobalamins. In sum, hypervitaminosis B12 denotes a disorder in the metabolism of vB12, and it could serve as a biomarker of a pathophysiological process with diagnostic and prognostic potential for various diseases.