Aplastic Anemia

Overview
  • Aplastic Anemia refers to a syndrome of bone marrow failure resulting in hypocellularity of the marrow and attendant pancytopenia, including anemia, thrombocytopenia, and neutropenia. A long list of etiologies, both inherited and acquired, can cause aplastic anemia although in the majority of patients the syndrome is idiopathic. Below we discuss in more detail some of the possible etiologies and then describe the predictable clinical consequences of pancytopenia.
Inherited Etiologies
  • Inherited etiologies are relatively rare and includes Fanconi Anemia.
Acquired Etiologies
  • Chemical and Drugs
    • A large variety of drugs and chemicals can arrest hematopoiesis and thus result in aplastic anemia. In some cases, bone marrow arrest is predictable and dose-related; however, in other cases marrow aplasia is an unpredictable idiosyncratic reaction.
    • Predictable, Dose-related: Benzene and chloramphenicol are a well-known culprits as well as a long list of chemotherapeutics.
    • Idiosyncratic: Penicillamine, gold salts, as well as others
  • Infections
    • Infectious causes of aplastic anemia are typically viral with Parvovirus a classic cause as well as occasionally EBV and CMV. For the sake of passing interest, most cases of viral marrow aplasia are due to an as yet unidentified viral (non-HAV/HBV/HCV) cause of viral hepatitis
  • Whole-body Radiation
    • Radiation Injury, either iatrogenic or otherwise, frequently causes bone marrow suppression and is often used prior to bone marrow transplantation to destroy the host marrow.
  • Idiopathic
    • For the majority of patients, no cause of marrow failure can be identified. The current thought is that bone marrow failure in these patients is likely secondary to some autoimmune process as immunosuppressive medications improve marrow production.
Clinical Consequences
  • The clinical consequences of aplastic anemia are predictable given the resultant pancytopenia. In most cases, the onset of symptoms is insidious, reflecting the half-lives of blood components and the degree of marrow failure. The presentation in any given patient will also depend on which blood line is most affected.
  • Anemia: The resultant normocytic anemia yields the classic complex of symptoms discussed on the anemia page, including fatigue, dyspnea on exertion, and light-headedness, among others
  • Neutropenia: Neutropenic patients can display profound infection susceptibility
  • Thrombocytopenia: Extremely low platelet levels can result in ecchymoses and petechia