Permanent abnormal dilation of bronchi with chronic infection and inflammation.
Also known as: bronchiectasis, chronic suppurative lung disease, tram-tracking
Overview
Irreversible dilation and thickening of medium-sized bronchi resulting from chronic inflammation and recurrent infection, producing chronic productive cough, recurrent exacerbations, and progressive lung damage.
Epidemiology
Underdiagnosed but increasingly recognized — prevalence ~50-500 per 100,000 in the US. More common in older women and those with prior respiratory infection or underlying lung disease. Cystic fibrosis is a major cause in younger patients.
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Question 1PulmonaryEasy
A 24-year-old woman with cystic fibrosis (CF) has chronic cough, copious purulent sputum, and recurrent infections. HRCT shows airway dilation greater than the accompanying artery, lack of bronchial tapering, and mucus plugging. Which underlying mechanism best explains these structural findings?
ADefective ciliary dynein arms impairing mucociliary transport
BAirway smooth muscle hypertrophy with subepithelial fibrosis
CSelf-perpetuating cycle of poor clearance, infection, inflammation
EParenchymal fibrosis exerting radial traction on airways
Why Self-perpetuating cycle of poor clearance, infection, inflammation is correct
Bronchiectasis is permanent abnormal dilation of the bronchi caused by a self-perpetuating cycle (Cole's vicious cycle): an initial airway insult impairs mucociliary clearance, predisposing to bacterial colonization and chronic infection, which provokes neutrophilic inflammation and proteolytic enzyme (neutrophil elastase) release, causing further airway wall destruction and dilation
Why the others are wrong
Defective ciliary dynein arms impairing mucociliary transport — dynein arm defects are the mechanism of primary ciliary dyskinesia; in cystic fibrosis (CF) the clearance defect comes from CFTR-mediated airway surface liquid dehydration with thick tenacious secretions, and the cilia themselves are structurally normal
Airway smooth muscle hypertrophy with subepithelial fibrosis — this describes asthmatic airway remodeling, which produces largely reversible airflow obstruction rather than the permanent bronchial dilation and mucus plugging on this HRCT
Neutrophil elastase excess driving airway wall destruction — elastase proteolysis is a downstream step inside the vicious cycle rather than the underlying defect, and alone it cannot explain the impaired clearance and chronic infection that drive this patient's mucus plugging
Parenchymal fibrosis exerting radial traction on airways — traction bronchiectasis also shows dilated, non-tapering airways on HRCT, but it occurs in fibrotic interstitial lung disease such as idiopathic pulmonary fibrosis, where retracting fibrotic lung pulls airways open, rather than in CF, where copious purulent sputum and mucus plugging reflect the infection-inflammation cycle
Additional high-yield points
Common causes of bronchiectasis include cystic fibrosis (CF), primary ciliary dyskinesia, post-infectious damage, allergic bronchopulmonary aspergillosis (ABPA), and immunodeficiencies
High-resolution CT (HRCT) findings: signet-ring sign (airway-to-artery ratio >1), lack of tapering, and visible peripheral airways are characteristic
Question 2PulmonaryMedium
A 42-year-old woman has years of daily cough with large amounts of purulent sputum and recurrent pneumonias. High-resolution CT shows dilated bronchi with thickened airway walls. Which of the following is the most likely diagnosis?
ALung abscess with cavitation
BSevere persistent asthma
CBronchiectasis from infection
DChronic obstructive bronchitis
EIdiopathic pulmonary fibrosis
Reveal answer & full explanation
Correct answer: C — Bronchiectasis from infection
ALung abscess with cavitation
BSevere persistent asthma
CBronchiectasis from infection✓
DChronic obstructive bronchitis
EIdiopathic pulmonary fibrosis
Why Bronchiectasis from infection is correct
Years of copious purulent sputum with recurrent pneumonias plus HRCT showing permanently dilated, thick-walled bronchi is bronchiectasis.
The irreversibly dilated airways trap mucus and cripple mucociliary clearance, setting up a vicious cycle of colonization and reinfection.
The CT finding (signet-ring/tram-track airways larger than the accompanying vessel) is diagnostic.
Why the others are wrong
Idiopathic pulmonary fibrosis — IPF causes a progressive dry cough with basilar reticulation and honeycombing, not purulent sputum and dilated bronchi; this is the wrong-CT-pattern trap.
Chronic obstructive bronchitis — Chronic bronchitis produces sputum but does not create the fixed bronchial dilation seen on CT; missing that structural finding is the symptom-overlap trap.
Lung abscess with cavitation — An abscess is a focal, subacute cavity with an air-fluid level in one segment, not years of daily sputum with diffusely dilated, thick-walled airways on HRCT.
Severe persistent asthma — asthma also causes chronic cough and can thicken the airway walls on CT, but its hallmark is variable wheeze with reversible airflow obstruction, not years of copious purulent sputum and recurrent pneumonias; permanently dilated bronchi on HRCT define bronchiectasis even when it coexists with asthma; this is the airway-wall-overlap trap.
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Vicious cycle of impaired mucociliary clearance, chronic bacterial colonization (Pseudomonas, H. influenzae, S. aureus, Moraxella, NTM), neutrophilic inflammation, and bronchial wall destruction. Permanent bronchial dilation, fibrosis, and loss of elastic recoil follow.
Clinical presentation
Symptoms
Chronic productive cough with copious mucopurulent sputum (often daily, worse in morning)
Recurrent respiratory infections / exacerbations
Dyspnea, wheezing, fatigue
Hemoptysis (variable; ranges from blood-streaked sputum to massive)
Parallel linear opacities from thickened bronchial walls running peripherally
Cystic / varicose bronchi
Saccular dilations with or without air-fluid levels (severe disease)
Lack of bronchial tapering
Bronchus stays as wide as its parent for more than 2 cm beyond a branch point
Airways visible near the pleura
Bronchi seen within 1 cm of the costal pleura
Mucus plugging
Tree-in-bud or 'finger-in-glove' opacities (supportive finding)
HRCT findings of bronchiectasis (signet-ring sign, lack of tapering and airways within 1 cm of the pleura are diagnostic; wall thickening and mucus plugging are supportive).
Treatment
First-line
Airway clearance — cornerstone of therapy: chest physiotherapy, oscillating PEP devices (Acapella, Flutter), high-frequency chest wall oscillation vest, active cycle of breathing
Add nebulized hypertonic saline (3-7%) if sputum stays hard to clear despite airway clearance; dornase alfa for CF only (may worsen non-CF bronchiectasis)
Inhaled bronchodilator (albuterol) prior to airway clearance to ease maneuvers
Treat exacerbations with prolonged antibiotics (10-14 days), targeted to prior sputum cultures: amoxicillin-clavulanate, doxycycline; ciprofloxacin if Pseudomonas
Vaccinations: annual influenza, pneumococcal, COVID-19, RSV (single dose at age 50-74 with chronic lung disease such as bronchiectasis, or any adult ≥75), Tdap
Smoking cessation; pulmonary rehabilitation
Second-line / adjunct
Chronic macrolide therapy for frequent exacerbations despite airway clearance (azithromycin 250-500 mg 3×/week; erythromycin in BLESS) — reduces exacerbations (EMBRACE, BAT, BLESS trials); screen for QT prolongation and NTM before starting. Brensocatib (oral DPP-1 inhibitor, FDA-approved 2025 after the ASPEN trial) also reduces exacerbations and is the first drug approved specifically for non-CF bronchiectasis
Inhaled antibiotics for chronic Pseudomonas: tobramycin, aztreonam, colistin (off-label in non-CF)
HRCT signet-ring sign — bronchial lumen larger than adjacent pulmonary artery — is the imaging hallmark of bronchiectasis.
Always look for a reversible cause: CF testing in younger patients, immunoglobulins, alpha-1 level, ABPA workup, NTM, HIV.
Pseudomonas isolation predicts more rapid lung function decline and worse prognosis; consider chronic inhaled antibiotic.
Rule out NTM infection BEFORE starting chronic azithromycin — monotherapy in NTM-positive patients selects resistance.
Sweat chloride ≥60 mmol/L is diagnostic of CF; 30-59 mmol/L intermediate (genetic testing needed); <30 mmol/L unlikely.
References
BTS 2019 — British Thoracic Society Guideline for Bronchiectasis in Adults (Hill et al., Thorax 2019)
ERS 2025 — European Respiratory Society Clinical Practice Guideline for the Management of Adult Bronchiectasis (Chalmers et al., Eur Respir J 2025;66:2501126)
EMBRACE Trial — Azithromycin for Prevention of Exacerbations in Non-CF Bronchiectasis (Wong et al., Lancet 2012)
BLESS Trial — Long-term Erythromycin for Bronchiectasis (Serisier et al., JAMA 2013)
ASPEN Trial — Phase 3 Trial of the DPP-1 Inhibitor Brensocatib in Bronchiectasis (Chalmers et al., NEJM 2025)
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