Vitamin B12 deficiency

Vitamin B^sub 12^ is an essential cofactor that is integral to methylation processes important in reactions related to DNA and cell metabolism, thus a deficiency may lead to disruption of DNA and cell metabolism and thus have serious clinical consequences. Intracellular conversion of vitamin B^sub 12^ to two active coenzymes, adenosylcobalamin in mitochondria and methylcobalamin in the cytoplasm, is necessary for the homeostasis of methylmalonic acid and homocysteine, respectively. Methylmalonic acid is converted into succinyl-CoA, of which vitamin B^sub 12^ is a cofactor for the reaction. Homocysteine is biosynthesized from rnethionine then resynthesized into methionine or converted into amino acid cysteine. Vitamin B^sub 12^ deficiency is relatively common, with important and variable clinical consequences. Here, Hunt et al present a concise summary of the most up to date evidence on how to diagnose and manage vitamin B^sub 12^ deficiency.