What are the drug and idiosyncratic etiologies of anemia?

Updated: Nov 26, 2019
  • Author: Joseph E Maakaron, MD; Chief Editor: Emmanuel C Besa, MD  more...
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Drugs or chemicals commonly cause the aplastic and hypoplastic group of disorders. Certain types of these causative agents are dose related and others are idiosyncratic. Any human exposed to a sufficient dose of inorganic arsenic, benzene, radiation, or the usual chemotherapeutic agents used for treatment of neoplastic diseases develops bone marrow depression with pancytopenia.

Conversely, among the idiosyncratic agents, only an occasional human exposed to these drugs has an untoward reaction resulting in suppression of one or more of the formed elements of bone marrow (1:100 to 1:millions). With certain types of these drugs, pancytopenia is more common, whereas with others, suppression of one cell line is usually observed. Thus, chloramphenicol may produce pancytopenia, whereas granulocytopenia is more frequently observed with toxicity to sulfonamides or antithyroid drugs.

Current evidence suggests that susceptibility to idiosyncratic reactions involves certain genetic polymorphisms involving cellular detoxifying enzymes. As a result, exogenous toxins that would normally be converted to nontoxic compounds are instead metabolized into reactive compounds that  modify cellular proteins, which can be recognized by the immune system and trigger autoimmunity. [4]

The idiosyncratic causes of bone marrow suppression include multiple drugs in each of the categories that can be prefixed with anti- (eg, antibiotics, antimicrobials, anticonvulsants, antihistamines). The other idiosyncratic causes of known etiology are viral hepatitis and paroxysmal nocturnal hemoglobinuria. In approximately one half of patients presenting with aplastic anemia, a definite etiology cannot be established, and the anemia must be regarded as idiopathic.

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