Aspergillosis

Aspergillosis is a spectrum of diseases caused by fungi of the genus Aspergillus, with Aspergillus fumigatus being responsible for approximately 90 percent of invasive infections. Aspergillus species are ubiquitous saprophytic molds found in soil, decaying vegetation, compost heaps, air-conditioning systems, and construction/renovation sites. The organism reproduces by releasing conidia (asexual spores) that are 2 to 3 micrometers in diameter, small enough to reach the terminal bronchioles and alveoli when inhaled. Immunocompetent individuals inhale hundreds of Aspergillus conidia daily without developing disease because the innate immune system provides robust protection through multiple layers of defense. Airway epithelial cells trap conidia in the mucociliary blanket, alveolar macrophages phagocytose and kill germinating conidia through oxidative burst mechanisms (reactive oxygen species), and neutrophils destroy hyphal forms through degranulation and extracellular trap formation. Aspergillosis develops when these defense mechanisms are compromised or overwhelmed. The clinical spectrum of aspergillosis includes four major forms: invasive pulmonary aspergillosis (IPA), chronic pulmonary aspergillosis (CPA), allergic bronchopulmonary aspergillosis (ABPA), and aspergilloma. Invasive pulmonary aspergillosis is the most life-threatening form, occurring almost exclusively in severely immunocompromised patients. The primary risk factors...