Deficiency of the 'intrinsic factor of Castle' causes:

Answer is B (Pernicious Anemia) Deficiency of Intrinsic factor leads to a specific form of vitamin B12 deficiency megaloblastic anemia called `Pernicious Anemia'. Pernicious Anemia also known as Addison's Anemia is a megaloblastic anemia due to deficiency of intrinsic factor (secreted by parietal cells of gastric mucosa) that is essential for vitamic B12 absorption. Note: 'Intrinsic factor' was first described by castle & coworkers and hence intrinsic factor is also called Intrinsic factor of Castle.