Question
Aspergillosis
Answer
Aspergillosis encompasses a spectrum of diseases caused by Aspergillus species (most commonly A. fumigatus), a ubiquitous environmental mould with septate hyphae showing characteristic acute-angle (45°) branching — distinguishing it microscopically from the broader, non-septate, wide-angle-branching hyphae of the Mucorales.
Clinical spectrum (determined largely by host immune status):
- Allergic Bronchopulmonary Aspergillosis (ABPA) — a hypersensitivity reaction to Aspergillus colonizing the airways, occurring in atopic/asthmatic or cystic fibrosis patients, without tissue invasion; presents with wheeze, eosinophilia, raised total and Aspergillus-specific IgE.
- Aspergilloma (“fungus ball”) — a non-invasive mass of fungal hyphae colonizing a pre-existing lung cavity (e.g., from old healed tuberculosis), can cause haemoptysis.
- Invasive Pulmonary Aspergillosis — angioinvasive, life-threatening infection in severely immunocompromised (neutropenic) patients, causing tissue infarction/necrosis from vascular invasion.
Laboratory diagnosis: direct microscopy (KOH mount) showing septate, acute-angle-branching hyphae; culture on Sabouraud dextrose agar (rapid growth, characteristic conidiophore/conidial head morphology for species identification); galactomannan antigen test (serum/BAL) — useful for diagnosing invasive aspergillosis in high-risk neutropenic patients; (1,3)-beta-D-glucan — a less specific fungal cell-wall marker; histopathology showing tissue invasion (for invasive disease); high-resolution CT chest showing characteristic findings (e.g., “halo sign” in early invasive disease).
Treatment: voriconazole is the first-line agent for invasive aspergillosis; amphotericin B as an alternative; surgical resection for aspergilloma with significant haemoptysis; corticosteroids (± antifungal) for ABPA.