Aspergillus

Transmission
  • Aspergillus refers to a fungal genus encompassing a variety species whose spores are ubiquitously found in nature. Inoculation of humans occurs through respiratory inhalation of spores.
Clinical Consequences
  • Overview
    • A healthy immune system can easily eliminate germinating spores of inhaled aspergillus. Consequently, disease caused by growing fungi is only observed in those with reduced immunity. However, some healthy individuals can develop an allergic reaction to inhaled spores.
  • Allergic Aspergillosis
    • Some healthy, immunocompetent individuals can develop an allergic, extrinsic asthma to aspergillus spores. This is mediated by a Type I Hypersensitivity reaction to fungal spores resulting in the development of aspergillus-specific IgE.
  • Aspergilloma
    • Aspergillus spores can germinate and grow inside large pathologic spaces within the lung. These balls of Aspergillus hyphae are termed "Aspergillomas" and can cause result in cough and hemoptysis. These large, pathologic spaces may be the sequelae of cavitary pulmonary tuberculosis lesions or due to emphysema. In general, the fungus does not grow beyond the borders of the cavity in those with normal immunity.
  • Invasive Aspergillosis
    • Invasive Aspergillosis almost exclusively occurs in immunocompromised patients. The fungus may initially invade through the lung resulting in expanding necrotizing lesions. In some individuals the organism may spread hematogenously and can infect virtually any organ.
  • Hepatocellular Carcinoma
    • In passing we mention that certain aspergillus species can produce the potent hepatotoxin "Aflatoxin". Human exposure to aflatoxin occurs following ingestion of Aspergillus-contaminated grains or nuts and can induce development of hepatocellular carcinoma. It is important to note that the pathogenesis is not due to any infection of the fungi but purely through ingestion of pre-formed Aflatoxin.
Treatment