Hematopoietic and Lymphatic Tissues
Cells of the hematopoietic and lymphatic tissues serve vital functions of host defense, internal homeostasis, and bodily intactness. They all originate from the same stem cell population and in their functional activities interact in various ways (see chapter 1). Disorders in one cell population may thus cause reactions in the other. For this reason, the hematopoietic and lymphatic systems are discussed together. Just as there are a large number of different cell populations with various differentiation stages and functional activities, so are there a multitude of human diseases of the blood and lymphatic systems. The most common and important are discussed in this chapter. The most common leading symptoms of all these diseases are infection, hemorrhage or thrombosis, and anemia.
Red Blood Cell Disorders
Red blood cell (RBC) disorders manifest themselves by either a decrease (anemia) or an increase (erythrocytosis) of RBCs, the latter being reactive or neoplastic in nature. These disorders preferentially affect oxygen transport to tissues; excessive erythrocytosis may be complicated by increased intravascular thrombosis.
White Blood Cell Disorders (Nonlymphatic)
White blood cell (WBC) disorders (nonlymphatic) include reactive and neoplastic changes of hematopoietic tissues. Reactive changes may be either hyperplastic (leukocytosis) or hypoplastic/aplastic (leukopenia). They arise in response to exogenous or endogenous stimuli and generally are reversible. Neoplastic changes (myelodysplastic or myeloproliferative syndromes, leukemia) also may occur in response to certain stimuli (e.g., carcinogens, radiation, viral infection) but become autonomous and thus practically irreversible.
Nonneoplastic Lymphatic Disorders
Lymphatic tissues are the body’s main carriers of host defense, both specific and nonspecific. Consequently, nonneoplastic changes in the lymphatic system may result from functional alterations in the immune system as well as from inflammatory, necrotic, or metabolic disorders. Changes in lymph nodes or spleen may be secondary to other disorders, as when the lymph system or bloodstream transports disease products from a primary disease focus (e.g., lymphadenitis in the neck developing secondary to a dental abscess or septic splenitis secondary to bacterial enterocolitis). Investigation of a patient with some form of lymphatic disease therefore must always include a search for a primary cause.
Neoplastic Lymphatic Disorders
Malignant neoplasias of the lymphatic tissues are collectively identified as malignant lymphomas (MLs) or, when malignant cells circulate in the blood, lymphocytic leukemias. There are 2 major groups of MLs: Hodgkin lymphomas (lymphogranulomatosis) and non-Hodgkin lymphomas (NHLs). Hodgkin lymphoma, or Hodgkin disease (HD), is distinguished from NHL by its polymorphic features, including certain inflammatory components such as fibrosis and occasional regression simulating nonneoplastic diseases, which eventually may progress to ML. Although it is a lymphatic malignancy, it is accompanied by a large number of associated nonneoplastic cells, which may influence the course and progression of the disease. NHL, by contrast, begins as malignant clonal proliferations. Transition from HD to NHL and combinations of HD with certain types of NHL have been observed (HD and chronic lymphocytic leukemia [CLL] or follicular center cell lymphoma [FCC]; see Table 10-4).
TABLE 10-1
Category | RBCs | Characteristics |
Blood loss, acute | Initially: normochromic, normocyticLater: hypochromic reticulocytosis | Acute volume depletionRBC reduction secondary to fluid influxRapid RBC regeneration |
Blood loss, chronic | Hypochromic | Reduced iron stores |
Increased Destruction of Erythrocytes | ||
Hemolytic anemias | Features of hemolysis and tissue siderosisBone marrow: significant erythropoietic hyperplasiaSplenomegaly | |
Immunologic | Reticulocytosis | Autoantibodies against RBC (infection or drug induced)Isohemagglutinins (transfusion induced, erythroblastosis fetalis) |
Mechanical | Schistocytes | Microangiopathic: Hemolytic uremic syndrome Thrombotic thrombocytopenic purpura Trauma by intracardiac artificial devices Multiple hemangiomas (e.g., hepatic) |
Hereditary | SpherocytosisElliptocytosisSickle cellsHypochromic, microcyticHeinz bodies | RBC membrane and cytoskeleton deficienciesHemoglobinopathies: sickle cell anemia, thalassemiaEnzyme deficiencies (e.g., of hexose monophosphate shunt) |
Deficient Erythropoiesis | ||
“Stem cell” defect | Normochromic,Normocytic to mildly macrocytic | Aplastic anemia (with pancytopenia), pure red cell aplasia secondary to myelofibrosis (with thrombocytopenia, splenomegaly) |
Maturation defect | MegaloblasticAnisocyticHypochromicPoikilocytic | Pernicious anemia (vitamin B12 deficiency), folate deficiency, anemia, iron deficiency (infection, tumor, chronic blood loss) |
Hb synthesis defect | Sideroblasts | Sideroblastic anemia |
normochromic: normal color (i.e. normal Hb content); normocytic: normal size and shape of RBC; hemolytic: red cell lysis
TABLE 10-2
REACTIVE HEMATOPOIETIC HYPERPLASIA (NONLYMPHATIC)
Involved Cell Compartment | Cause |
Erythrophilic, neutrophilic, and megakaryopoiesis | Blood loss or transient myelotoxic agents |
Preferentially neutrophilic | Pyogenic bacterial infections, extensive tissue necroses |
Less extensive: drugs such as SCF, steroids | |
Neutrophilic and histiocytic (frequently with lymphocytes and eventual granuloma formation) | Chronic infections such as by intracellular organisms (e.g., Rickettsia, Yersinia, Salmonella, mycobacteria), mycoses, collagen-vascular diseases (e.g., lupus erythematosus) |
Preferentially histiocytic | Protozoal infection (e.g., malaria) |
Suggestive viral infection (hemophagocytic syndrome) | |
Phagocytosis defects (infantile septic granulomatosis, Chediak-Higashi syndrome, and others) | |
Metabolic (various storage diseases: morbus Gaucher, morbus Niemann-Pick, and others) | |
Eosinophilic | Allergic diseases |
Parasitic infestations | |
Viral infections with immune complex reaction (e.g., Hodgkin disease) | |
Treatment with IL-2 | |
Basophilic | Certain allergic diseases (e.g., food allergies) |
Certain endocrine disorders (e.g., myxedema) | |
Estrogen treatment |
SCF indicates colony stimulating factor; IL, interleukin.
TABLE 10-3
CLASSIFICATION IN SUBTYPES OF ACUTE MYELOPROLIFERATIVE DISEASES*
FAB Class | Subtype Name | Abbreviation | Proportion of Acute Myeloproliferative Diseases (%) |
M0 | Acute myeloblastic leukemia, stem cell (i.e., minimal differentiation) | AML | 3-5 |
M1 | Acute myeloblastic leukemia without maturation | AML | 15-20 |
M2 | Acute myeloblastic leukemia with maturation | AML | 25-30 |
M3 | Acute promyelocytic leukemia | APL | 5-20 |
M4 | Acute myelomonocytic leukemia | AMML | 20-30 |
M5 | Acute monoblastic leukemia | AMOL | 2-9 |
M6 | Acute erythroleukemia | AEL | 3-5 |
M7 | Acute megakaryoblastic leukemia | 3-12 |
FAB indicates French-American-British classification.
*Acute myeloproliferative diseases are clonal neoplastic disorders of hematopoietic stem cells, the classification of which is determined by their preferential cytologic differentiation.
Adapted from Hoffman R et al. Hematology. Philadelphia: Churchill-Livingstone; 2000.
TABLE 10-4
CLASSIFICATION OF LYMPHOMA (NHL) ENTITIESRevised European American Lymphoma (REAL) Classification
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