Introduction to Plastic Bronchitis in Children

Plastic bronchitis is a rare but potentially life-threatening condition characterized by the formation of large, branching bronchial casts that obstruct the airways. It primarily affects children, especially those with underlying cardiopulmonary conditions. The term "plastic" refers to the cohesive and rubber-like consistency of the casts, not their composition.

Key points:

• Incidence: Rare, exact prevalence unknown
• Age of onset: Typically in children, but can occur in adults
• Gender predilection: No significant difference
• First described: 1901 by Bettmann

Etiology of Plastic Bronchitis

The etiology of plastic bronchitis is multifactorial and often associated with underlying conditions:

1. Cardiac conditions:
   • Fontan circulation (most common)
   • Other congenital heart diseases
2. Respiratory conditions:
   • Asthma
   • Cystic fibrosis
   • Allergic bronchopulmonary aspergillosis
3. Lymphatic disorders:
   • Lymphangiectasia
   • Lymphangiomatosis
4. Infections:
   • Influenza
   • Bacterial pneumonia
5. Idiopathic cases (no identifiable cause)

Pathophysiology of Plastic Bronchitis

The pathophysiology of plastic bronchitis involves complex interactions between the lymphatic system, bronchial mucosa, and inflammatory processes:

1. Cast formation:
   • Accumulation of proteinaceous material in the airways
   • Fibrin exudation and mucin production
   • Incorporation of inflammatory cells and cellular debris
2. Lymphatic involvement:
   • Abnormal lymphatic drainage or leakage into airways
   • Increased central venous pressure (in Fontan circulation)
3. Inflammatory cascade:
   • Release of pro-inflammatory cytokines
   • Recruitment of inflammatory cells
   • Increased mucus production
4. Airway obstruction:
   • Progressive cast formation leading to partial or complete obstruction
   • Impaired mucociliary clearance

Clinical Presentation of Plastic Bronchitis

The clinical presentation of plastic bronchitis can vary from mild respiratory symptoms to acute respiratory distress:

• Respiratory symptoms:
  • Chronic cough (often productive)
  • Wheezing
  • Dyspnea
  • Chest pain
• Expectoration of casts:
  • Large, branching bronchial casts (pathognomonic)
  • May be accompanied by hemoptysis
• Acute presentations:
  • Sudden onset of respiratory distress
  • Cyanosis
  • Hypoxemia
• Associated symptoms:
  • Fever (if infectious etiology)
  • Fatigue
  • Weight loss (in chronic cases)

Diagnosis of Plastic Bronchitis

Diagnosis of plastic bronchitis requires a high index of suspicion and a combination of clinical, radiological, and pathological findings:

1. Clinical evaluation:
   • Detailed history (including underlying conditions)
   • Physical examination (auscultation for decreased breath sounds)
2. Imaging studies:
   • Chest X-ray: Atelectasis, infiltrates, or hyperinflation
   • CT scan: Tree-in-bud opacities, bronchial filling defects
   • MRI lymphangiography: Evaluate lymphatic anomalies
3. Bronchoscopy:
   • Visualization and removal of casts
   • Bronchoalveolar lavage for cytology and microbiology
4. Cast analysis:
   • Gross examination: Branching, rubbery appearance
   • Histopathology: Classification into inflammatory or acellular types
5. Additional tests:
   • Pulmonary function tests
   • Echocardiography (to evaluate cardiac function)
   • Serum IgE and eosinophil count (if allergic etiology suspected)

Treatment of Plastic Bronchitis

Treatment of plastic bronchitis is multifaceted and depends on the underlying etiology:

1. Acute management:
   • Airway clearance: Bronchoscopic removal of casts
   • Supportive care: Oxygen therapy, mechanical ventilation if needed
2. Pharmacological interventions:
   • Mucolytics: N-acetylcysteine, dornase alfa
   • Bronchodilators: Beta-2 agonists
   • Corticosteroids: Systemic or inhaled
   • Antibiotics: If bacterial infection suspected
3. Management of underlying conditions:
   • Cardiac: Optimization of Fontan circulation
   • Respiratory: Asthma control, cystic fibrosis management
   • Lymphatic: Thoracic duct ligation, embolization
4. Novel therapies:
   • Inhaled tissue plasminogen activator (tPA)
   • Aerosolized heparin
   • Sirolimus (for lymphatic anomalies)
5. Supportive measures:
   • Chest physiotherapy
   • Nutritional support
   • Psychosocial support for patients and families

Prognosis of Plastic Bronchitis

The prognosis of plastic bronchitis varies depending on the underlying etiology and treatment response:

• Mortality:
  • Historically high (up to 50% in some series)
  • Improved with modern management techniques
• Recurrence:
  • Common, especially in cardiac-related cases
  • May require long-term management
• Factors influencing prognosis:
  • Underlying condition (cardiac vs. non-cardiac)
  • Frequency and severity of exacerbations
  • Timely diagnosis and intervention
  • Response to treatment
• Long-term outcomes:
  • Potential for chronic respiratory impairment
  • Impact on quality of life
  • Need for ongoing medical surveillance