Plastic Bronchitis

Plastic bronchitis is a rare condition in which rubbery, branching casts of the bronchial tree form and obstruct the airways. It occurs mainly in children, and in adults with asthma or inflammatory lung disease.

Two types are described. The inflammatory (cellular) type, with eosinophil and neutrophil rich casts, follows asthma, allergic bronchopulmonary aspergillosis, infection (influenza, pneumonia), and acute chest syndrome in sickle cell disease. The non-inflammatory (acellular) type, with casts of fibrin and lymph, is linked to congenital heart disease, especially after Fontan surgery, and to lymphatic flow disorders.

Pathophysiology. In the inflammatory type, mucus, fibrin and cells form from airway inflammation and exudation. In the acellular type, raised central venous pressure and abnormal lymphatic flow lead to leakage of lymph into the airway, where it clots.

Cough that produces branching casts (diagnostic), wheeze, chest tightness, dyspnoea, fever and, in severe cases, hypoxaemia with respiratory distress. Chest examination may show absent breath sounds over a lobe, with wheeze.

Acute respiratory distress from a large cast blocking the main airway is an emergency.

• The expectorated or removed cast, with analysis: fibrin and mucin with eosinophils (inflammatory type), or fibrin with few cells (acellular type), and culture for infection.
• Chest radiograph and CT: lobar collapse, patchy opacities, and in the acellular type, features of heart disease and lymphatic leakage.
• Flexible or rigid bronchoscopy to remove casts and confirm the diagnosis.
• Cardiac evaluation in children and adults with congenital heart disease: echocardiography, catheterisation and Fontan pressures.
• Lymphatic imaging in the acellular type: dynamic contrast magnetic resonance lymphangiography or lymphoscintigraphy, to find abnormal pulmonary lymphatic flow.
• Look for asthma, ABPA (aspergillus IgE, total IgE, eosinophils), sickle cell disease and infection as underlying causes.

Differential diagnosis.

• Foreign body aspiration
• Mucus plugging in asthma without casts
• Bronchial tumour
• Pneumonia with lobar collapse
• Pulmonary haemorrhage with clots

• Acute airway obstruction: rigid or flexible bronchoscopic removal of casts, with oxygen and ventilatory support.
• Inflammatory type: treat the cause. Prednisolone 0.5 to 1 mg/kg daily (maximum 40 to 60 mg) for 5 to 14 days, nebulised salbutamol 2.5 mg, inhaled corticosteroid, azithromycin 250 mg daily or 10 mg/kg three times weekly in children, and antibiotics for infection. In ABPA add itraconazole 200 mg twice daily.
• Mucolytic and fibrinolytic inhalation: nebulised acetylcysteine 3 to 5 mL of 10% solution, and dornase alfa 2.5 mg nebulised once or twice daily. Nebulised heparin 5000 units every 4 to 6 hours and nebulised alteplase 5 mg every 6 to 8 hours have been used in small series, and carry a bleeding risk, so they need monitoring.
• Acellular type: optimise cardiac function and lower systemic venous pressure (Fontan optimisation, pulmonary vasodilator such as sildenafil), low fat diet with medium chain triglycerides, and lymphatic interventions (selective lymphatic embolisation, thoracic duct embolisation) in specialist centres. Heart transplantation for refractory disease.
• Airway clearance with physiotherapy, and a plan for early bronchoscopy at recurrence.
• Sickle cell disease: oxygen, analgesia, antibiotics, and exchange transfusion for severe acute chest syndrome.

Complications and prognosis. Recurrent obstruction, respiratory failure and death in severe cases. Recurrence is common, and outcome in acellular disease depends on the cardiac and lymphatic disease.

Monitoring. Review every 1 to 3 months in recurrent disease, with symptom diary, spirometry and bronchoscopy for relapse.

Referral and escalation. Refer to a paediatric or adult respiratory service with bronchoscopy, and to cardiology and lymphatic specialists for the acellular type. Refer as an emergency for airway obstruction.