Aspergillosis

Aspergillosis is an infection or allergic response caused by fungi of the genus Aspergillus, commonly affecting the respiratory system, and ranging from allergic reactions to invasive disease in immunocompromised individuals.

Definition

Epidemiology

Ubiquitous fungi found in soil, decaying vegetation, and indoor environments
Incidence higher in immunocompromised patients (hematologic malignancies, transplant recipients)
Allergic bronchopulmonary aspergillosis (ABPA) affects 1–2% of asthmatics and up to 15% of cystic fibrosis patients
Invasive aspergillosis has high mortality (~30–90%) in immunocompromised hosts
Chronic pulmonary aspergillosis occurs mostly in patients with underlying lung disease

Etiology

Aspergillus species, most commonly Aspergillus fumigatus, A. flavus, A. niger
Exposure via inhalation of airborne conidia
Immunocompromised state: neutropenia, corticosteroid therapy, organ transplantation
Chronic lung disease: tuberculosis, COPD, sarcoidosis
Allergic predisposition: asthma or cystic fibrosis
Environmental exposure in damp or moldy settings

Pathophysiology

Inhaled conidia evade mucociliary clearance and germinate in susceptible hosts
Immune response varies: allergic (ABPA), chronic (CPA), or invasive (IA)
Invasive aspergillosis involves tissue invasion, angioinvasion, and necrosis
Allergic forms involve exaggerated IgE-mediated immune response
Chronic forms involve granulomatous inflammation and cavitary lung lesions
Host immune status determines severity and clinical manifestation
Pathogenesis includes interplay between fungal virulence factors and host defenses