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.

Allergic bronchopulmonary aspergillosis (ABPA) is caused by an allergic reaction to the common mold aspergillus

Congenital (genetic) causes.

Cystic fibrosis, which is associated with increased mucus production.

Cause: Autosomal recessive CFTR (CF transmembrane regulator) gene mutation resulting in impaired chloride ion channel function. Key complications: 1. Pulmonary infections: diffuse bronchiectasis, chronic productive cough, recurrent pulmonary infections (eg, (ABPA)). 2. Pancreatic insufficiency: malabsorption w/steatorrhea, fat-soluble vitamin def., chronic pancreatitis. 3. Male infertility. 4. Additional: newborn jaundice, digit clubbing, sinusitis, nasal polyps, weight loss. Diagnosis: Pilocarpine sweat test shows increased chloride (Cl-) concentration. CFTR gene mutation testing.

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.

Asthma and/or COPD also produces favorable conditions for bronchiectasis.

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.

Hemoptysis, as a result of airway neovascularization and rupture.

Lung crackles, rhonchi, wheezes.

Digit clubbing.

In digit clubbing, the ends of the digits are enlarged and rounded; note that this is less commonly reported today.

Hypoxemia, due to airway obstruction. Pulmonary hypertension and right heart failure.

Exacerbations are defined as worsening symptoms that last two days or longer, and require changes in treatment approach. Exacerbations are especially problematic because they cause additional bronchial damage.

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.

Chronic infection results in chronic inflammation with neutrophilic and T-cell infiltration.

These inflammatory cells release cytokines that cause tissue destruction and airway remodeling.

Neutrophil elastase (NE) is a key inflammatory protease released by neutrophils cited in tissue destruction in multiple chronic inflammatory pulmonary diseases, including bronchiectasis.

Over time, this degradation of the bronchial wall produces dilation.

And, chronic infection and inflammation further impair mucociliary clearance.

Despite the fact that medium-sized airways are dilated in bronchiectasis, they can also become obstructed by recurrent inflammation and infection and mucus accumulation.

Furthermore, smaller, downstream airways, which significantly impact airflow, can become obstructed by the inflammation and infections.

These airway abnormalities lead to hypoxemia and right heart failure.

For References, please see full tutorial on Bronchiectasis and Bronchiolitis.

Bronchiectasis

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