• Clinical science

Aspergillosis

Summary

Aspergillosis is the collective term for diseases caused by mold species in the genus Aspergillus. Aspergillus spores are ubiquitous but do not usually cause infection in immunocompetent individuals. Risk factors for Aspergillus infection include immunosuppression (e.g., HIV, hematologic malignancies, transplant recipients) and underlying pulmonary conditions (e.g., cavernous tuberculosis, COPD). Infections may be localized, causing asymptomatic pulmonary aspergilloma, or symptomatic, complicated infiltrates (e.g., with cavitation, fibrosis, or necrosis). In immunocompromised patients, invasive aspergillosis is common, which manifests as severe pneumonia and septicemia with potential involvement of other organs. In patients with pre-existing bronchopulmonary conditions (e.g., asthma, cystic fibrosis), Aspergillus may cause allergic bronchopulmonary aspergillosis (ABPA), which presents with asthmatic symptoms or sinusitis. Elevated serum IgE levels and eosinophilia indicate a fungal infection. Tissue biopsy followed by histopathology and culture are used to confirm the diagnosis. Medical treatment for aspergillosis infection includes voriconazole, caspofungin, or amphotericin B. An aspergilloma, on the other hand, must be surgically removed. ABPA is primarily managed with glucocorticoid therapy. Immunocompromised patients should receive prophylactic posaconazole.

Etiology

References:[1][2]

Clinical features

Allergic bronchopulmonary aspergillosis (ABPA)

Chronic pulmonary aspergillosis

Invasive aspergillosis

Invasive aspergillosis mostly infects the bronchioles of the lungs, but can also manifest as a disseminated infection (e.g., in skeletal, cutaneous, or neurological tissue)!

References:[1][2][3][4][5][6]

Diagnostics

ABPA

Chronic pulmonary aspergillosis

  • Aspergilloma
    • X-ray and CT
      • Monad sign: a peripheral air crescent around a fungus ball in a pre-existing lung cavity
      • Radiological evidence of a mobile fungus ball
        • The mobility of the fungus ball is demonstrated by moving the patient from a supine position to a prone or lateral recumbent position.
      • The upper lobe is mostly affected because of the increased concentration of oxygen
    • Laboratory tests: positive sputum culture or positive Aspergillus IgG serology
  • Aspergillus nodule
    • X-ray and CT: multiple nodules
    • Laboratory tests: positive biopsy result or positive Aspergillus IgG serology
  • Cavitary pulmonary aspergillosis

Invasive aspergillosis

  • Initial work-up
    • Chest CT
      • Multiple nodules
      • Halo sign: hemorrhagic ground glass opacities around nodules
      • Sickle-shaped air crescents around the fungal colony
    • Serum assays
    • If CNS infection is suspected: cranial MRI
  • Confirmatory test: positive culture and/or histopathological evidence of invasive aspergillosis
    • Specimen collection
      • Bronchoalveolar lavage via bronchoscopy
      • In patients with peripheral nodular lesions on imaging: endobronchial lung biopsy via bronchoscopy or CT-guided percutaneous biopsy
    • Findings

References:[2][4][7][8][9][10]

Differential diagnoses

Differential diagnosis of pulmonary fungal infections
Mycoses Etiology Clinical features Diagnosis Treatment

Aspergillosis

Coccidioidomycosis (Valley fever)
  • Serology: increased IgM ; increased IgG at 1–3 months
  • KOH staining on smears: dimorphic fungus and spherules filled with endospores
  • Confirmatory: culture
Paracoccidioidomycosis
  • Infected patients often asymptomatic
  • Acute pneumonia
  • Painful nasal, pharyngeal, and laryngeal mucosal ulcerations
  • Lymphadenopathy (usually cervical)
  • Can disseminate → extrapulmonary manifestations (including verrucous skin lesions)
  • KOH staining on smears : budding yeast with “captain's wheel” appearance
  • Cultures have a low sensitivity
Blastomycosis
  • Infected patients often asymptomatic
  • Pneumonia with flulike symptoms
  • Can disseminate → extrapulmonary manifestations (verrucous skin lesions, lytic bone lesions, genitourinary involvement , CNS lesions )
  • KOH staining on smears : broad-based dimorphic fungus
  • Confirmatory: culture
Histoplasmosis
  • Pathogen: Histoplasma capsulatum
  • Risk factors: AIDS, exposure to bird or bat droppings especially in Mississippi and Ohio river valleys
  • Infected patients often asymptomatic
  • Acute pneumonia
  • Can disseminate → extrapulmonary manifestations
Cryptococcosis
Candidiasis
Pneumocystis pneumonia
  • Chest x-ray or CT: Diffuse, bilateral ground-glass opacities
  • Silver stain and immunofluorescence on bronchoalveolar lavage (or lung biopsy if sputum is negative): disc shaped-yeasts
  • Cannot be cultured


References:[11][12][13][14][15][16][17][18][19][20][21]

The differential diagnoses listed here are not exhaustive.

Treatment

ABPA

Pulmonary aspergillosis

Asymptomatic patients without disease progression do not require treatment, but regular follow-up with imaging and Aspergillosis antibody titer tests are nonetheless absolutely necessary.

Invasive aspergillosis

References:[4][5][22][23][24]