How should post‑infectious bronchiolitis obliterans be diagnosed and managed in a pediatric patient?

Post-Infectious Bronchiolitis Obliterans (PIBO) in Pediatric Patients

Post-infectious bronchiolitis obliterans in children should be diagnosed based on a history of severe respiratory infection (particularly adenovirus or Mycoplasma pneumoniae), persistent respiratory symptoms (chronic cough, wheezing, tachypnea), and characteristic findings on high-resolution CT showing air trapping, mosaic perfusion, and bronchial wall thickening, with treatment centered on systemic corticosteroids combined with azithromycin. 1, 2

Diagnosis

Clinical Presentation

• Look for a preceding severe respiratory infection, most commonly adenovirus (50% of cases) or Mycoplasma pneumoniae, followed by persistent respiratory symptoms that fail to resolve 1, 3
• Key symptoms include: repeated wheezing, chronic wet cough, tachypnea, dyspnea, and sputum production that persist beyond the acute infection phase 1, 2
• Physical examination reveals: diffuse crackles, signs of respiratory distress, and potentially signs of chronic hypoxemia 3
• Risk factors to identify: male sex, severe hypoxemia during initial infection, and requirement for mechanical ventilation 4

Radiological Diagnosis

High-resolution CT (HRCT) is the cornerstone imaging modality and should demonstrate: 1, 2

• Patchy ground-glass opacities (present in all cases)
• Mosaic perfusion pattern (areas of decreased attenuation)
• Bronchial wall thickening
• Bronchiectasis
• Air trapping on expiratory images
• Unilateral hyperlucent lung in severe cases 2, 5

Chest X-ray findings (less specific but useful for screening): 2, 5

• Pulmonary overinflation
• Patchy ground-glass opacity
• Unilateral hyperlucency of enlarged lung
• Mixed patterns of collapse, hyperlucency, and peribronchial thickening

Pulmonary Function Testing

• Demonstrates fixed airway obstruction (most common finding) 5
• Useful for monitoring therapeutic response and disease progression 1
• Shows obstructive pattern with reduced FEV1 and FEV1/FVC ratio
• May reveal air trapping with elevated residual volume 5

Bronchoscopy with BAL

• Bronchoalveolar lavage shows elevated neutrophils (46-90% of cells) 3
• Biopsy (when performed) reveals: lymphocytic inflammatory infiltrate and bronchiolar fibrosis 3
• Note: Biopsy is not routinely required for diagnosis when clinical history and HRCT are characteristic 5

Nocturnal Oximetry Assessment

• Reduced mean SpO2 (median 96.5%) and lower values (median 89%) 3
• Increased oxygen desaturation index (1.1-11.2 events/hour) 3
• Identifies patients requiring supplemental oxygen therapy 1

Management

Pharmacological Treatment

Primary therapy consists of systemic corticosteroids combined with azithromycin: 1, 2, 3

Corticosteroid Regimen

• Methylprednisolone 20-30 mg/kg IV for three consecutive days monthly for 6 months 3
• Alternative: Oral prednisone in combination with azithromycin for less severe cases 2
• This approach resulted in clinical improvement in 82% of patients (9/11) and radiological improvement in 64% (7/11) 3

Azithromycin Therapy

• Long-term low-dose azithromycin should be administered concurrently with steroids 1, 2
• Improves patient condition through anti-inflammatory and immunomodulatory effects 2
• Continue for extended duration (7-31 months in reported cases) 2

Supportive Care

• Home oxygen therapy for patients with persistent hypoxemia (required in approximately 14% of cases) 1
• Intensive management may be necessary for severe cases (required in 52% of cases) 1

Monitoring and Follow-Up

• Long-term follow-up is essential to detect complications including bronchiectasis and progressive obstructive airway disease 5
• Serial HRCT scans to assess radiological response (though improvement may lag behind clinical improvement) 2
• Repeat pulmonary function testing to evaluate therapeutic response and disease progression 1
• Follow-up duration: Minimum 7 months, with some patients requiring monitoring for years 2, 5

Important Clinical Pitfalls

Do not dismiss persistent respiratory symptoms after severe viral pneumonia - PIBO should be suspected when wheezing and respiratory symptoms persist beyond expected recovery 2, 4

Do not delay HRCT imaging - patchy ground-glass opacity on HRCT is a critical screening index for BO development and should prompt immediate evaluation 2

Do not withhold treatment pending biopsy confirmation - diagnosis can be made clinically with characteristic history and HRCT findings; biopsy carries risks and is not routinely necessary 5

Recognize the recent surge in cases - there has been a post-pandemic increase in PIBO cases (11 cases in 2023 vs. 6 cases in previous 7 years in one series), potentially related to changes in viral ecology and adenovirus genotypes 3

Understand treatment limitations - while steroids combined with azithromycin offer benefit, approximately 18-38% of patients show no significant improvement, and PIBO remains a disease with high morbidity requiring multidisciplinary management 2, 3, 4