Introduction
 
Erythrocyte production requires the presence of bone marrow stem cells, erythropoietin (EPO), elemental iron, vitamins, cytokines, and a suitable marrow microenvironment. Deficiency or unavailability of any of these key components may lead to the underproduction of erythrocytes and result in anemia. Normal erythropoiesis follows an ordered progression from the pluripotent colony-forming unit–granulocyteerythroid-monocyte macrophage (CFU-GEMM), to the burst-forming units–erythroid (BFU-E), to colony-forming units–erythroid (CFU-E), to proerythroblasts, to erythroblasts, and finally to mature erythrocytes (Figure 2-1). Red cell maturation is dependent on the presence of EPO, a 165 amino acid glycoprotein produced by the kidney. EPO acts via cross-linkage of its receptor. . . . [Full Text of this Article]


Underproduction anemias resulting from vitamin deficiencies
 
Iron
Iron deficiency anemia
Anemia of chronic inflammation/disease (dysregulation of iron)

Megaloblastic anemias
 
Cobalamin (vitamin B12) deficiency
Folic acid deficiency
Other causes of megaloblastic anemia
Nonmyelodysplastic sideroblastic anemias
Anemia from malnutrition and starvation

Underproduction anemias resulting from organ dysfunction
 
Renal disease
Anemia from other endocrine abnormalities
Anemia associated with gastrointestinal abnormalities
Anemia associated with liver disease

Marrow failure states leading to underproduction anemias
 
Pure red cell aplasia

Anemia secondary to marrow infiltration or abnormalities in the marrow microenvironment
 

Complex/multifactorial anemias
 
Anemia associated with pregnancy
Anemia of the elderly
Anemia of cancer
Anemia associated with HIV