What are the main causes of microcytic anemia?

Microcytic anemia is characterized by the presence of smaller-than-normal red blood cells and is primarily caused by inadequate hemoglobin production. The most common causes of microcytic anemia include iron deficiency and various forms of thalassemia.

Iron deficiency is a leading cause of microcytic anemia because iron is a crucial component of hemoglobin. When iron levels are insufficient, the body cannot produce adequate amounts of hemoglobin, resulting in smaller red blood cells. Thalassemia is a genetic disorder that affects hemoglobin production. In this condition, the synthesis of one of the globin chains is impaired, leading to reduced hemoglobin production and the formation of microcytic red blood cells.

In contrast, other causes listed in the question, such as vitamin B12 and folate deficiencies, typically result in macrocytic anemia, where the red blood cells are larger than normal. Chronic disease can contribute to anemia but usually leads to normocytic anemia rather than microcytic. Hemolysis, the destruction of red blood cells, and conditions like leukemia and lymphoma, generally do not directly cause microcytic anemia. Thus, the primary causes of microcytic anemia are accurately identified as iron deficiency and thalassemia.