This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
[{'content': 'Vitamin Bi2 deficiency results in: March 2013 \nSelect and explain. \nA. Aplastic anemia, B. Iron deficiency anemia, C. Anemic of chronic diseases, D. Macrocytic anemia', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. D i.e. Macrocytic anemiaMacrocytic anemia Especially common causes of macrocytic anemias are the so-called megaloblastic anemias, in which cells are larger because they cannot produce DNA quickly enough to divide at the right time as they grow, and thus grow too large before division.Causes for the DNA synthetic problem range from lack of ceain vitamins needed to produce DNA (notably folate and B12), to poisons or inhibitors of DNA replication, such as some kinds of antiviral drugs and chemotherapeutic agents.Classically these megaloblastic types of anemias are associated also with more specific features, such as megaloblasts in the bone marrow, the presence of ovalocytes in the (peripheral) blood smear, and the pathognomonic presence of hypersegmented neutrophils.', 'role': 'assistant'}]