Pancytopenia with markedly hypocellular marrow and normal marrow cell cytogenetics.
Incidence worldwide is 2 to 5 cases/million population per year and 5 to 12 cases/million population per year in the United States (and in other industrialized countries). Incidence is approximately twice as high in Asian countries.
Peak incidence between ages 15 and 25 and 65 to 69 years.
The definitions for range of severity of aplastic anemia are shown in Table 3–1.
Table 3–1Degree of Severity of Acquired Aplastic Anemia |Favorite Table|Download (.pdf) Table 3–1 Degree of Severity of Acquired Aplastic Anemia
|Diagnostic Categories ||Hemoglobin ||Reticulocyte Concentration ||Neutrophil Count ||Platelet Count ||Marrow Biopsy ||Comments |
|Moderately severe ||<100 g/L ||<40 × 109/L ||<1.5 × 109/L ||<50 × 109/L ||Decrease of hematopoietic cells. ||At the time of diagnosis at least 2 of 3 blood counts should meet these criteria. |
|Severe ||<90 g/L ||<30.0 × 109/L ||<0.5 × 109/L ||<30.0 × 109/L ||Marked decrease of hematopoietic cells. ||Search for a histocompatible sibling should be made if age permits. |
|Very Severe ||<80 g/L ||<20.0 × 109/L ||<0.2 × 109/L ||<20.0 × 109/L ||Marked decrease or absence of hematopoietic cells. ||Search for a histocompatible sibling should be made if age permits. |
ETIOLOGY AND PATHOGENESIS
Immune suppression of marrow by autoreactive T lymphocytes.
Toxic injury to stem and/or progenitor cells (e.g., certain chemotherapy or drugs) (see Table 3–2).
Inherited intrinsic stem cell defect (e.g., Fanconi anemia).
TABLE 3–2SOME DRUGS ASSOCIATED WITH MODERATE RISK OF APLASTIC ANEMIA* |Favorite Table|Download (.pdf) TABLE 3–2 SOME DRUGS ASSOCIATED WITH MODERATE RISK OF APLASTIC ANEMIA*
|Gold salts |
Acquired T lymphocyte mediated autoimmune suppression of hematopoietic stem cells and/or progenitor cells in most cases (~70%).
Paroxysmal nocturnal hemoglobinuria (PNH) (frequently associated with hypoplastic marrow).
Chemicals, e.g., benzene. Rare today in countries with workplace regulations limiting exposure.
Drugs, e.g., chloramphenicol (see Table 3–2 for most frequent offenders; see also ...
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