What laboratory findings indicate pernicious anemia or Vitamin B12 deficiency?

Pernicious anemia and Vitamin B12 deficiency are characterized by specific hematological findings. The hallmark laboratory finding in this condition is an increased mean corpuscular volume (MCV), which indicates that red blood cells are larger than normal—a condition known as macrocytosis. This macrocytic anemia occurs due to impaired DNA synthesis as a result of Vitamin B12 deficiency.

Additionally, a decreased level of Vitamin B12 in the serum is another critical indicator of this deficiency. Vitamin B12 is necessary for normal red blood cell production and neurological function, and its deficiency can lead to significant hematological and neurological consequences.

In contrast, the other choices do not align with the typical findings associated with pernicious anemia or Vitamin B12 deficiency. For instance, while decreased MCV may occur in iron deficiency anemia, it does not correlate with Vitamin B12 deficiency. Normal MCV and changes in ferritin or iron levels also do not indicate a Vitamin B12 deficiency; these findings are more characteristic of other types of anemia. Therefore, the combination of increased MCV and decreased B12 is indicative of pernicious anemia, making this the correct answer.