TCN2 and celiac disease: Yet, this nutritional deficiency can quickly appear with VB12 malabsorption in patients with PA, celiac disease, inflammatory bowel disease, Whipple’s disease, food-bound VB12 malabsorption, chronic alcoholism, patients taking antidiabetic medications (e.g., metformin) and bile acid sequestrants (e.g., cholestyramine), and patients with inherited disorders such as deficiency of the non-glycosylated protein of transcobalamin II (TC-II) [2,10,45–48].