Clinical meaning
Bronchiectasis is characterized by permanent, abnormal dilation of bronchi due to a vicious cycle of infection, inflammation, and structural airway damage. Cole's vicious cycle hypothesis describes how impaired mucociliary clearance (from ciliary dysfunction, mucus hyperviscosity, or airway damage) allows bacterial colonization, which triggers neutrophilic inflammation and release of proteases (neutrophil elastase, matrix metalloproteinases) that damage airway walls, causing further dilation and impaired clearance. Common predisposing conditions include post-infectious damage (childhood pneumonia, pertussis, measles, TB), cystic fibrosis (CFTR mutation), primary ciliary dyskinesia (dynein arm defects), immunodeficiency (common variable immunodeficiency — CVID), allergic bronchopulmonary aspergillosis (ABPA), and autoimmune diseases (RA, inflammatory bowel disease). The most common colonizing organisms are Haemophilus influenzae, Pseudomonas aeruginosa (associated with worse prognosis), and Moraxella catarrhalis.
Diagnosis & workup
Diagnostics & workup: - High-resolution CT chest (HRCT): definitive diagnostic test — bronchial dilation (signet ring sign: bronchus larger than adjacent artery), lack of bronchial tapering, bronchial wall thickening, mucus plugging, tree-in-bud opacities - Sputum culture and sensitivity: identify colonizing organisms (H. influenzae, P. aeruginosa, NTM) and guide antibiotic selection - PFTs: typically obstructive pattern (reduced FEV1/FVC); DLCO usually preserved - Immunoglobulin levels: IgG, IgA, IgM, IgG subclasses to screen for immunodeficiency - CF testing: sweat chloride test (> 60 mmol/L diagnostic) and/or CFTR genetic testing for adults < 40 - ABPA screening: total IgE, Aspergillus-specific IgE and IgG, CBC with eosinophil count - Alpha-1 antitrypsin level - Sputum for AFB and NTM cultures if clinical suspicion (MAC is common in 'Lady Windermere syndrome')