What is mucopurulent chronic bronchitis?

Mucopurulent Chronic Bronchitis

Mucopurulent chronic bronchitis is a specific form of chronic bronchitis characterized by chronic cough with purulent sputum production, resulting from bacterial colonization and infection of the airways in patients with underlying chronic bronchial inflammation. 1

Definition and Pathophysiology

Chronic bronchitis is clinically defined as chronic cough and sputum expectoration occurring on most days for at least 3 months of the year and for at least 2 consecutive years when other pulmonary or cardiac causes for the chronic productive cough are excluded 2. When this condition is accompanied by purulent sputum, it is classified as mucopurulent chronic bronchitis.

The pathophysiological hallmarks include:

• Mucous gland enlargement and goblet cell hyperplasia in the airways 1
• Reduction in serous acini of submucosal glands, decreasing production of antimicrobial factors (lactoferrin, antiproteases, lysozyme) 1
• Decreased number and length of cilia with squamous metaplasia 1
• Formation of continuous mucus blanket lining airways (versus discrete deposits in healthy airways) 1
• Bacterial colonization and growth in pooled secretions 1

Clinical Manifestations

The key clinical features of mucopurulent chronic bronchitis include:

• Chronic productive cough with purulent sputum
• Increased sputum volume (up to 100 mL/day more than normal) 1
• Recurrent exacerbations with increased sputum purulence 1
• Impaired mucociliary clearance 1
• Heightened cough reflex sensitivity 1
• Ineffective cough, especially when airflow obstruction is present 1

Pathogenic Mechanisms

The development of mucopurulent chronic bronchitis involves a vicious cycle:

1. Chronic inflammation (often from cigarette smoke exposure) causes mucous gland hyperplasia and goblet cell metaplasia 1, 2
2. Impaired mucociliary clearance leads to mucus retention 1
3. Bacterial colonization occurs in retained secretions 1
4. Bacterial exoproducts further damage cilia, stimulate mucus production, impair immune function, and destroy immunoglobulins 1
5. This cycle perpetuates inflammation and infection 1

Common bacterial pathogens include:

• Streptococcus pneumoniae
• Haemophilus influenzae (especially type B)
• Moraxella catarrhalis 1, 3

Exacerbations

Acute exacerbations of chronic bronchitis are characterized by:

• Increased sputum volume
• Increased sputum purulence
• Worsening shortness of breath 1

These exacerbations are often triggered by:

• Viral respiratory infections (rhinovirus, coronavirus, influenza B, parainfluenza) 1
• Bacterial superinfection 1, 3

Diagnosis

Diagnosis of mucopurulent chronic bronchitis requires:

• Documentation of chronic cough and sputum production for ≥3 months/year for 2 consecutive years 2
• Exclusion of other respiratory or cardiac causes of chronic productive cough 2
• Microscopic examination of sputum showing increased neutrophils and bacteria 3
• Assessment of exposure history to respiratory irritants, particularly cigarette smoke 2

Management Considerations

Management should focus on:

1. Smoking cessation - critical for slowing disease progression 4
2. Bronchodilator therapy - inhaled ipratropium bromide and sympathomimetic agents to relieve bronchospasm 4
3. Mucolytic agents - may reduce exacerbation frequency and days of disability 5, 6
4. Appropriate antibiotic therapy for acute exacerbations 3
5. Airway clearance techniques and respiratory muscle strengthening 4

Clinical Implications

The mucopurulent phenotype of chronic bronchitis carries important prognostic implications:

• Accelerated lung function decline
• Higher risk of respiratory infections
• Increased frequency of exacerbations 2

Common Pitfalls

• Underdiagnosis due to patient underreporting of symptoms 2
• Failure to distinguish acute exacerbations from other causes of respiratory deterioration (pneumonia, pulmonary embolism, heart failure) 1
• Inadequate duration of antibiotic therapy (10-14 days recommended for exacerbations) 3
• Overreliance on bronchodilators without addressing underlying inflammation and infection 4

Understanding mucopurulent chronic bronchitis as part of the spectrum of chronic bronchitis is essential for appropriate management and prevention of disease progression to more severe forms of COPD.