Certified Neuroscience Registered Nurse (CNRN) Practice Exam

What condition can result from a deficiency in vitamin B12?

1. Megaloblastic anemia

2. Iron-deficiency anemia

3. Sickle cell anemia

4. Thalassemia

The correct answer is: Megaloblastic anemia

Megaloblastic anemia is a condition characterized by the production of large, abnormal red blood cells due to an impairment in DNA synthesis. A deficiency in vitamin B12 disrupts this process, leading to the formation of these larger, less efficient cells. Vitamin B12 is crucial for the proper functioning of folate metabolism, which is essential for DNA synthesis and red blood cell formation. When the body lacks sufficient vitamin B12, the hallmark signs of megaloblastic anemia, such as fatigue, weakness, and pallor, can occur as a result of decreased red blood cell production and the presence of ineffective erythropoiesis. In contrast, iron-deficiency anemia is caused by a lack of iron, which is necessary for hemoglobin production. Sickle cell anemia is a genetic disorder affecting the structure of hemoglobin, and thalassemia involves genetic defects in hemoglobin production as well. Therefore, these conditions arise from different underlying mechanisms and not from a deficiency in vitamin B12.