What is the major type of leukocyte seen in the peripheral smear of a patient with aplastic anemia?

In patients with aplastic anemia, the bone marrow fails to produce sufficient blood cells, leading to a deficiency of all types of blood cells, including red blood cells, white blood cells, and platelets. As a result, the peripheral blood smear often shows a marked decrease in the number of granulocytes, which includes segmented neutrophils, eosinophils, and basophils, as well as a significant reduction in monocytes.

With the compensatory mechanisms working, lymphocytes become the predominant leukocyte observed in the peripheral smear under these circumstances. While their numbers may not be significantly elevated beyond normal levels, compared to the other types of cells that are significantly reduced, lymphocytes can appear more prevalent. It is important to note that the overall white blood cell count will be low in aplastic anemia, but lymphocytes often remain detectable in the peripheral blood, which accounts for their prevalence in the smear.

Therefore, the presence of lymphocytes as the major leukocyte in this context is a reflection of the pathophysiological state of aplastic anemia, where other leukocyte lineages are severely diminished.