What is the primary cause of aplastic anemia?

Aplastic anemia is primarily characterized by the failure of the bone marrow to produce adequate amounts of blood cells, which includes red blood cells (RBCs), white blood cells, and platelets. This condition arises due to damage to the hematopoietic stem cells in the bone marrow, which leads to significantly reduced production of all types of blood cells, resulting in pancytopenia.

The primary cause of this decreased bone marrow production can be attributed to several factors, including autoimmune disorders, exposure to chemicals or toxins, certain medications, radiation, and viral infections. In aplastic anemia, the deficiency in blood cell production leads to symptoms such as fatigue, increased risk of infections, and a higher tendency to bleed due to the low levels of red cells, white cells, and platelets.

The other answer choices refer to conditions that do not accurately describe the pathophysiology of aplastic anemia. For instance, decreased intake of iron is associated with iron deficiency anemia, while an inability to absorb vitamin B12 is linked to megaloblastic anemia. An increased rate of RBC destruction is related to hemolytic anemia. These options do not pertain to the underlying mechanism of bone marrow failure seen in aplastic anemia.