Aspergillosis
Epidemiology and Etiology:
- Immunocompromised
- Significant cause of morbidity and death in the
immunocompromised host
- Most common invasive mold worldwide
- Second most common fungal pathogen after Candida
- More common than Candida in the lung
- Aspergillus fumigatus is the most often seen species in the clinical lab
Common sites:
Gross features:
Histologic features:
- There are many Aspergillus look-alikes in tissue
(Fusarium, Paecilomyces,
Acremonium, Bipolaris,
Pseudallescheria boydii,
Scedosporium apiospermum)
- it is important to defer to culture whenever
possible
- Septate hyphae
- Dichotomously branched at 45-degree angle
- Uniform, consistent width (3-6 um) without
constrictions at points of septation
- Fruiting heads maybe within cavities (this is the
ONLY feature permitting firm diagnosis at the genus level)
- Oxalate crystals (polarizing) are an important
clue when hyphae cannot be identified
Immunophenotype:
Marker:
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Sensitivity:
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Specificity:
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Molecular features:
Other features:
- Colonizing or saprophytic form:
- Intrabronchial and pre-existing cavity fungus ball
- Hypersensitivity form:
- Allergic bronchopulmonary aspergillosis
- Mucoid impaction of bronchi
- Hypersensitivity pneumonitis
- Allergic bronchopulmonary aspergillosis
- Eosinophilic pneumonia
- Bronchocentric granulomatosis
- Invasive (immunocompromised patients usually):
- Acute invasive aspergillosis
- Necrotizing pseudomembranous
- Tracheobronchitis
- Chronic necrotizing pneumonia
- Bronchopleural fistula
- Empyema
- Minimally invasive-chronic necrotizing:
- Angioinvasive-disseminated (neutropenia often):
- Intravascular spread resulting in hemorrhagic
infarcts
- Some cases defy categorization, or show overlap
between the above patterns
References:
- Leslie, ed. Practical Pulmonary Pathology – A Diagnostic
Approach. 2nd ed.
(2011)