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Blood cells play essential roles in oxygenation of tissues, coagulation, protection against infectious agents, and tissue repair. Blood cell deficiency is a relatively common occurrence that can have profound repercussions. Anemia, a deficiency in oxygen-carrying erythrocytes, is either classified as microcytic, due to an insufficient supply of iron, or macrocytic often due to a deficiency of either vitamin B12 or folic acid. Pharmacologic treatment of these types of anemia usually involves replacement of the missing substance. An alternative therapy for certain types of anemia and for deficiency in other types of blood cells is administration of recombinant hematopoietic growth factors, which stimulate the production of various lineages of blood cells and regulate blood cell function.

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High-Yield Terms to Learn
Cobalamin Vitamin B12
ESAs Erythropoiesis-stimulating agents
dTMP synthesis A set of biochemical reactions that produce deoxythymidylate (dTMP), an essential constituent of DNA synthesis. The cycle depends on the conversion of dihydrofolate to tetrahydrofolate by dihydrofolate reductase.
G-CSF Granulocyte colony-stimulating factor, a hematopoietic growth factor that regulates production and function of neutrophils
GM-CSF Granulocyte-macrophage colony-stimulating factor, a hematopoietic growth factor that regulates production of granulocytes (basophils, eosinophils, and neutrophils), and other myeloid cells
Hemochromatosis A condition of chronic excess total body iron caused either by an inherited abnormality of iron absorption or by frequent transfusions to treat certain types of hemolytic disorders (eg, thalassemia major)
Macrocytic anemia A group of anemias with various etiologies, characterized by abnormally large erythrocytes. Divided into megaloblastic and nonmegaloblastic subtypes, based on bone marrow findings. Megaloblastic anemia is most often due to folate or vitamin B12 deficiency.
Microcytic anemia A deficiency in serum hemoglobin and erythrocytes in which the erythrocytes are abnormally small. Often caused by iron deficiency
Neutropenia An abnormally low number of neutrophils in the blood; patients with neutropenia are susceptible to serious infection
Pernicious anemia A form of megaloblastic anemia resulting from deficiency of intrinsic factor, a protein produced by gastric mucosal cells and required for intestinal absorption of vitamin B12
Thrombocytopenia An abnormally low number of platelets in the blood; patients with thrombocytopenia are susceptible to hemorrhage


A. Iron and Vitamin Deficiency Anemias

Microcytic hypochromic anemia, caused by iron deficiency, is the most common type of anemia. Megaloblastic anemias are a subset of the macrocytic anemias and are caused by a deficiency of vitamin B12 or folic acid, cofactors required for the normal maturation of red blood cells. Pernicious anemia, the most common type of vitamin B12 deficiency anemia, is caused by a defect in the synthesis of intrinsic factor, a protein required for efficient absorption of dietary vitamin B12, or by surgical removal of that part of the stomach that secretes intrinsic factor.

B. Other Blood Cell Deficiencies

Deficiency in the ...

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