American Board of Surgery Qualifying Exam (ABS QE) Practice Test

Megaloblastic anemia can be caused by the deficiency of which vitamin?

1. Thiamine

2. Cobalamin

3. Pyridoxine

4. Ascorbic acid

The correct answer is: Cobalamin

Megaloblastic anemia is characterized by the presence of large, immature, and dysfunctional red blood cells in the bone marrow and peripheral blood. This condition is primarily caused by deficiencies in certain vitamins that are crucial for DNA synthesis and cell division. Cobalamin, also known as vitamin B12, plays a vital role in the formation of red blood cells and in the synthesis of DNA. It is especially important for proper cellular maturation and division. A deficiency in cobalamin leads to impaired DNA synthesis, resulting in the production of megaloblastic red blood cells. Patients with cobalamin deficiency often present with symptoms of anemia, fatigue, and neurological manifestations due to its involvement in the production of myelin, which insulates nerve fibers. In contrast, thiamine, pyridoxine, and ascorbic acid are essential vitamins that serve different biochemical functions, primarily related to energy metabolism and antioxidant activity, but they do not play a direct role in DNA synthesis and red blood cell maturation. Their deficiencies can lead to other disorders but not specifically to megaloblastic anemia. Thus, the correct association with megaloblastic anemia is indeed with a deficiency of cobalamin.