Allergic bronchopulmonary aspergillosis

Allergic bronchopulmonary aspergillosis (ABPA) is a condition characterised by an exaggerated response of the immune system (a hypersensitivity response) to the fungus Aspergillus (most commonly Aspergillus fumigatus). It occurs most often in people with asthma or cystic fibrosis. Aspergillus spores are ubiquitous in soil and are commonly found in the sputum of healthy individuals. A. fumigatus is responsible for a spectrum of lung diseases known as aspergilloses. ABPA causes airway inflammation, leading to bronchiectasis—a condition marked by abnormal dilation of the airways. Left untreated, the immune system and fungal spores can damage sensitive lung tissues and lead to scarring. The exact criteria for the diagnosis of ABPA are not agreed upon. Chest X-rays and CT scans, raised blood levels of IgE and eosinophils, immunological tests for Aspergillus together with sputum staining and sputum cultures can be useful. Treatment consists of corticosteroids and antifungal medications. Almost all patients have clinically diagnosed asthma, and present with wheezing (usually episodic in nature), coughing, shortness of breath and exercise intolerance (especially in patients with cystic fibrosis). Moderate and severe cases have symptoms suggestive of bronchiectasis, in particular thick sputum production (often containing brown mucus plugs), as well as symptoms mirroring recurrent infection such as pleuritic chest pain and fever. Patients with asthma and symptoms of ongoing infection, who do not respond to antibiotic treatment, should be suspected of ABPA. Aspergillus spores are small (2–3 μm in diameter) and can penetrate deep into the respiratory system to the alveolar level. In healthy people, innate and adaptive immune responses are triggered by various immune cells (notably neutrophils, resident alveolar macrophages and dendritic cells) drawn to the site of infection by numerous inflammatory cytokines and neutrophilic attractants (such as CXCR2 receptor ligands).