Megaloblastic anemia is characterized by what abnormality in red blood cells?

Megaloblastic anemia is characterized by the presence of larger-than-normal red blood cells, known as megaloblasts. This abnormality occurs primarily due to deficiencies in vitamin B12 or folate, both of which are critical for proper DNA synthesis and red blood cell formation. As a result of impaired DNA replication, the red blood cells produced are not able to divide normally, leading to the characteristic increase in size.

The larger red blood cells can lead to various complications, including decreased oxygen transport and potential blockage of small blood vessels. In contrast, other types of anemia might present with smaller red blood cells (microcytic anemia) or a normal cell size but with reduced hemoglobin content. In megaloblastic anemia, the increase in size reflects underlying issues with cellular synthesis and maturation, specifically related to folic acid or vitamin B12 deficiency.