Transcobalamin deficiency (TC) is a disorder of cobalamin transport that usually presents during the first few months of life and is characterized by megaloblastic anemia, failure to thrive, vomiting, weakness and pancytopenia. The disease is Transcobalamin deficiency (Orphanet rare-disease nomenclature entry Orphanet_859). Also known as: Inherited deficiency of transcobalamin, Transcobalamin II deficiency.