Which of the following is NOT a cause of non-megaloblastic macrocytic anemia?

Pernicious anemia is characterized by a deficiency of vitamin B12 due to poor absorption, often linked to autoimmune conditions affecting intrinsic factor production. It results in megaloblastic macrocytic anemia, where red blood cells are larger than normal due to impaired DNA synthesis.

In contrast, non-megaloblastic macrocytic anemia refers to conditions where macrocytosis occurs without the megaloblastic changes seen in pernicious anemia. Causes of non-megaloblastic macrocytic anemia include liver disease and alcohol use—both of which can lead to alterations in red blood cell production and morphology without affecting DNA synthesis. Hemolytic anemia is also generally associated with normocytic or microcytic anemia, but in certain chronic cases may lead to macrocytic red blood cells due to compensatory bone marrow response.

Thus, identifying that pernicious anemia is the condition that causes megaloblastic macrocytic anemia helps clarify why it is not included among the non-megaloblastic causes of macrocytic anemia.