Definition:

Vitamin B12 deficiency anaemia is caused by intestinal malabsorption of cobalamin. Imerslund-Grasbeck syndrome (IGS) is an autosomal recessive disorder characterized by juvenile megaloblastic anaemia and neurological symptoms such as peripheral neuropathy, cognitive problems, and dementia. If untreated, the disease is fatal. Biallelic mutations either in the cubilin (CUBN) or amnionless (AMN) gene cause IGS. Both proteins are involved in intestinal absorption and renal tubular reabsorption. Hereditary intrinsic factor deficiency (IFD) is a phenotype that is caused by mutations in CBLIF, the gene encoding intrinsic factor.