PRINCIPLES OF TOXICOLOGY

TABLE 4.2 Leukemias and Lymphomas
4.3 THE MYELOID SERIES: ERYTHROCYTES, PLATELETS, GRANULOCYTES
(NEUTROPHILS), MACROPHAGES, EOSINOPHILS, AND BASOPHILS
Red Blood Cells (RBC): Erythrocytes
4.3 THE MYELOID SERIES 91
ICD No. General Description
ICD 200: lymphosarcoma and reticulosarcoma Lymphocytic lymphomas involving resident
lymphocytes in various tissues such as the liver,
spleen, lung, skin, bone marrow, and gastrointestinal
tract
ICD 201: Hodgkin’s disease Lymph node cancers exhibiting Reed–Sternberg cells
ICD 202: other malignant neoplasms of lymphoid and Involves resident macrophage cell types located in the
histiocytic tissue
peripheral tissues such as lymph nodes, spleen, skin,
liver, and connective tissue
ICD 203: multiple myeloma Cancer of a specific plasma cell (antibody producing B
lymphocyte)
ICD 204: lymphoid leukemia Cancer of circulating B and T lymphocytes
ICD 205: myeloid leukemia Cancer of the myeloid series, usually granulocytes
(neutrophils or PMNs)
ICD 206: monocytic leukemia Cancers of the monocytic series involving the bone
marrow–derived monoblast
ICD 207: erythroleukemia Cancer of RBC precursors
ICD 208: leukemia not otherwise specified
Source: International Classification of Disease (ICD), 9th ed.
During erythrocyte maturation, the blast forming unit-erythrocyte or BFU-E matures into the colony
forming unit-erythrocyte (CFU-E), which finally evolves into a mature erythrocyte after extrusion of
the nucleus and acquisition of hemoglobin and a mature cytoskeletal support system. Accelerated
erythrocyte formation due to anemia, may result in the release of RBCs prior to the loss of the nucleus.
These immature erythrocytes known as reticulocytes can be found circulating in the blood in increased
numbers (i.e., reticulocytosis). Physicians may suspect anemia or a bleeding disorder if the number of
reticulocytes exceeds their normal blood level (normal circulating reticulocyte levels are 5 percent of
the total number of RBCs) or if other clinical parameters are abnormal, specifically, the number of
RBCs, the percent volume of packed RBCs or the hemoglobin content. Once the red blood cell is
released into circulation, it has a normal lifespan of 120 days. Damaged or senescent RBCs are
sequestered in the spleen and destroyed by splenic macrophages.
Mature RBCs are discoid-shaped and devoid of a nucleus and mitochondria. They are rich in the
heme-containing protein, hemoglobin, which transports oxygen to peripheral tissues and carries carbon
dioxide from the periphery to the lungs, where it is exhaled. Erythrocytes also provide a pH buffering
function by converting carbon dioxide to carbonic acid via the enzymatic activity of carbonic
anhydrase. Erythrocytes possess an outer membrane supported by a complex cytoskeletal system of
various proteins that are essential for carrying out the normal functions of the RBC. Erythrocytes
normally constitute around 40 percent by volume of whole blood and number around 3,500,000–
5,000,000 per cubic millimeter. The normal hemoglobin content of 100 mL of blood is 14 g. When
the 120-day lifespan of erythrocytes is shortened to the extent that stimulated erythrocyte replacement
cannot keep pace, varying degrees of anemia may result.
There are numerous causes of anemia, including abnormal hemoglobin inherited in the form of
sickle cell anemia or thalassemia; congenital nonspherocytic anemias involving defects in biochemical
pathways in the RBC (e.g., glucose-6-phosphate dehydrogenase deficiency); congenital spherocytosis,