Although not significant when corrected for multiple testing, eight single nucleotide polymorphisms (SNPs) in two genes, transcobalamin II (TCN2) and the transcobalamin II-receptor (TCblR), were found to influence several clinical traits of cobalamin deficiency.
Complete absence of TC-II or total functional abnormality causes tissue vitamin B12 deficiency resulting in a severe disease with megaloblastic anemia and immunologic and intestinal abnormalities in the first months of life.