Bronchiectasis
Bronchiectasis and Bronchiolitis
Overview
Bronchiectasis refers to a disease of elastic, muscular, and cartilaginous tissue destruction with resultant dilation & fibrosis in the setting of chronic airway infection and inflammation. It is primarily an adult-onset disease.
It is a chronic, heterogeneous disorder caused by repeated bouts of infection and inflammation that cause permanent dilation of the medium and medium-large airways.
The damage can be diffuse, as in the case of cystic fibrosis-related bronchiectasis, or focal, as in the case of local infection/abscess.
Etiologies
Idiopathic
Obstruction, which causes focal bronchiectasis, and can be due to tumor masses or foreign bodies in the bronchi.
Infection
Often bacterial; common pathogens include:
- Immune deficiencies
- Autoimmune disorders - for example, bronchiectasis is associated with inflammatory bowel disease and rheumatoid arthritis.
- Cystic fibrosis, which is associated with increased mucus production.
- Alpha-1-anti-trypsin deficiency, which results in increased unopposed proteolytic activity, predominantly via neutrophil elastase.
- Primary ciliary dyskinesia (aka, Kartagener syndrome) and Young syndrome, which are associated with impaired mucociliary function.
Symptoms/Complications
Cough with prominent sputum production.
- The sputum itself is often described as thick and "tenacious."
- Some patients have so-called "dry" bronchiectasis – this is often associated with nontuberculous mycobacterial infection, and is characterized by less sputum production.
- In digit clubbing, the ends of the digits are enlarged and rounded; note that this is less commonly reported today.
Diagnostic Findings
Chest X-Ray is often normal early on. Later findings of cysts and thickened airways (tram-tracking).
Chest CT findings: signet-ring sign, tram-tracking, honeycombing, string of pearls, bunch of grapes.
Treatments
Airway clearance techniques: cough assist, high frequency chest wall oscillation
Chest physiotherapy and postural drainage.
Macrolides and other antibiotics
Hyperosmolar and mucolytic agents that transform mucus to facilitate clearance
Anti-inflammatory drugs (corticosteroids)
Pathogenesis: A Vicious Cycle
Impaired mucociliary clearance and retention of airway secretions creates an environment vulnerable to chronic infection.
- Cystic fibrosis, primary ciliary dyskinesia (aka, Kartagener syndrome) and Young syndrome are associated with impaired mucociliary function.
- Neutrophil elastase (NE) is a key inflammatory protease released by neutrophils cited in tissue destruction in multiple chronic inflammatory pulmonary diseases, including bronchiectasis.