Agents Used in Anemias; Hematopoietic Growth Factors

Agents Used in Anemias; Hematopoietic Growth Factors

Hematopoiesis, the production from undifferentiated stem cells of circulating erythrocytes, platelets, and leukocytes, is a remarkable process that produces over 200 billion new blood cells per day in the normal person and even greater numbers of cells in people with conditions that cause loss or destruction of blood cells. The hematopoietic machinery resides primarily in the bone marrow in adults and requires a constant supply of three essential nutrients—iron, vitamin B₁₂, and folic acid—as well as the pres-ence of hematopoietic growth factors, proteins that regulate the proliferation and differentiation of hematopoietic cells. Inadequate supplies of either the essential nutrients or the growth factors result in deficiency of functional blood cells. Anemia, a deficiency in oxygen-carrying erythrocytes, is the most common and several forms are easily treated. 

Sickle cell anemia, a condition resulting from a genetic alteration in the hemoglobin molecule, is common but is not easily treated. It is discussed in the Box: Sickle Cell Disease and Hydroxyurea. Thrombocytopenia and neutropenia are not rare, and some forms are amenable to drug therapy. In this section, we first consider treatment of anemia due to deficiency of iron, vitamin B₁₂, or folic acid and then turn to the medical use of hematopoietic growth factors to combat anemia, thrombocytopenia, and neutrope-nia, and to support stem cell transplantation.

CASE STUDY

A 65-year-old woman with a long-standing history of poorly con-trolled type 2 diabetes mellitus presents with increasing numbness and paresthesias in her extremities, generalized weakness, a sore tongue, and gastrointestinal discomfort. Physical examination reveals a frail-looking, pale woman with diminished vibration sensation, diminished spinal reflexes, and a positive Babinski sign. Examination of her oral cavity reveals Hunter’s glossitis, in which the tongue appears deep red in color and abnormally smooth and shiny due to atrophy of the lingual papillae. Laboratory testing reveals a macrocytic anemia based on a hematocrit of 30% (normal for women, 37–48%), a hemoglobin concentration of 9.4 g/dL (normal for elderly women, 11.7–13.8 g/dL), an ery-throcyte mean cell volume (MCV) of 123 fL (normal, 84–99 fL), an erythrocyte mean cell hemoglobin concentration (MCHC) of 34% (normal, 31–36%), and a low reticulocyte count. Further laboratory testing reveals a normal serum folate concentration and a serum vitamin B12 (cobalamin) concentration of 98 pg/mL (normal, 250–1100 pg/mL). Results of a Schilling test indicate a diagnosis of pernicious anemia. Once megaloblastic anemia was identified, why was it important to measure serum concentrations of both folic acid and cobalamin? Should this patient be treated with oral or parenteral vitamin B12?