GENES AND CELL METABOLISM: Edited by Anastasia Z. Kalea and Dorothy Klimis-ZacasImmunodeficiency and inborn disorders of vitamin B12 and folate metabolismWatkins, Davida,b,c; Rosenblatt, David S.a,b,cAuthor Information aDepartment of Human Genetics, McGill University bDepartment of Specialized Medicine, Division of Medical Genetics, McGill University Health Centre cResearch Institute of the McGill University Health Centre, Montreal, Quebec, Canada Correspondence to David Watkins, PhD, Research Institute of the McGill University Health Centre, Child Health and Human Development, 1001 Decarie Blvd, Room E01-2389, Montreal, QC, Canada H4A 3J1. Tel: +1 514 934 1934x42973; e-mail: firstname.lastname@example.org Current Opinion in Clinical Nutrition and Metabolic Care: July 2020 - Volume 23 - Issue 4 - p 241-246 doi: 10.1097/MCO.0000000000000668 Buy Metrics Abstract Purpose of review Immune dysfunction, including severe combined immunodeficiency, has been described in genetic disorders affecting the metabolism of the vitamins cobalamin (vitamin B12) and folate. We have reviewed reports of clinical findings in patients with a number of inborn errors of cobalamin or folate metabolism, specifically looking for immune problems. Recent findings There is little evidence that immune function is affected in most of the disorders. Exceptions are Imerslund–Gräsbeck syndrome and hereditary folate malabsorption (affecting intestinal absorption of cobalamin and folate, respectively), transcobalamin deficiency (affecting transport of cobalamin in blood and cellular cobalamin uptake), and methylenetetrahydrofolate dehydrogenase 1 deficiency (catalyzing cytoplasmic interconversion of reduced folate coenzyme derivatives). Summary Although some inborn errors of cobalamin or folate can be associated with immune dysfunction, the degree and type of immune dysfunction vary with no obvious pattern. Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.