Hypersegmented neutrophils are most characteristic of which condition?

Hypersegmented neutrophils are a hallmark finding in megaloblastic anemia, which can be caused by either folate deficiency or vitamin B12 deficiency. In megaloblastic anemia, the impaired DNA synthesis leads to ineffective hematopoiesis, resulting in larger than normal red blood cells (macrocytes) and characteristic changes in white blood cell morphology, particularly in neutrophils.

When examining neutrophils in this context, you may observe that the nuclei of these cells are hypersegmented, meaning they have more than the typical number of lobes—often five or more. This alteration reflects the underlying issue with DNA synthesis, which is common to both folate and vitamin B12 deficiencies.

While both deficiencies lead to similar hematological findings, it is important to note that they can coexist and that hypersegmented neutrophils are not exclusive to one deficiency over the other. In iron deficiency anemia, however, such findings are absent, as this condition typically presents with microcytic, hypochromic red blood cells and normal neutrophil morphology. Thus, recognizing that hypersegmented neutrophils can arise from either folate or vitamin B12 deficiency is key, explaining why the correct answer encompasses both deficiencies.