USMLE

Aspergillis fumigatus

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Fungi
  1. Histoplasma
  2. Blastomyces
  3. Coccidioides
  4. Paracoccidioides
  5. Tinea (Dermatophytes)
  6. Malassezia
  7. Candida albicans
  8. Aspergillis fumigatus
  9. Cryptococcus neoformans
  10. Mucor and Rhizopus
  11. Pneumocystis jirovecii
  12. Sporothrix schenckii

Summary

Aspergillus is a genus of fungi that includes the species Aspergillus flavus, fumigatus, and parasiticus. Aspergillus is visually characterized by its narrow, filamentous hyphae or mold-form, with septations and acute-angle branching. The fungi commonly grows on decaying vegetation like crops and food, where it can cause disease by inhalation of spores or by ingestion of carcinogenic toxins. Direct infections with aspergillus can present in 3 ways: invasive aspergillus, aspergillomas, and allergic bronchopulmonary aspergillosis.

Invasive aspergillosis usually affects immunocompromised patients and is characterized by the fungal invasion of the lung and other organs and the formation of granulomas. Voriconazole is the first-line treatment for patients with invasive aspergillosis.

In contrast, Aspergillomas are balls or masses of fungus that can grow in pre-existing lung cavities. These may be seen in immunocompetent patients, as the only need is a pre-existing hole for the fungus to grow in. Aspergillomas are treated by surgical removal.

Finally, ABPA, or allergic bronchopulmonary aspergillosis, is an asthma-like hyper-sensitivity reaction to aspergillus that is treated with corticosteroids. 

Besides direct infections caused by the fungus itself, aspergillus can also cause disease indirectly by way of producing aflatoxins. These aflatoxins are ingested and reach the liver to cause hepatocellular carcinoma.

Key Points

  • Aspergillus fumigatus 
    • Includes A. flavus, A. fumigatus, and A. parasiticus
    • Characteristics
      • Fungi that exists in mold form only
        • Narrow septate hyphae
        • Branches at (acute) 45º angle
    • Transmission
      • Grows on decaying vegetation
        • E.g. leaves, vegetables, corn, soybeans, peanuts, compost
    • Presentation and Treatment
      • Invasive aspergillosis
        • Usually affects immunocompromised patients
        • Formation of lung granulomas
        • Treat with voriconazole (or isavuconazole)
      • Aspergillomas
        • Fungus balls in pre-existing lung cavities (especially after TB infection)
      • Allergic bronchopulmonary aspergillosis (ABPA)
        • Asthma-like hypersensitivity response
        • Treat with corticosteroids
    • Complications
      • May produce aflatoxins
        • Associated with hepatocellular carcinoma