Bronchiolitis Obliterans

Bronchiolitis obliterans (BO) is a chronic small-airway disease, not the acute viral bronchiolitis seen in infants. In children, it most often follows a severe lower-respiratory infection such as adenovirus, respiratory syncytial virus, influenza, or Mycoplasma pneumoniae. The injured bronchiolar lining heals with inflammation and scar formation, so the child develops persistent obstruction and air trapping rather than a brief, self-limited episode of wheezing. The bedside pattern is persistent cough, exertional dyspnoea, reduced exercise tolerance, or wheezing that continues after the original infection has resolved. Paediatric postinfectious BO is supported by three linked findings: a compatible antecedent infection; post-bronchodilator spirometry showing fixed obstruction, with FEV1/FVC below 0.70, less than 12% reversibility, and at least a 10% decline in FEV1 from baseline; and high-resolution CT showing mosaic attenuation, expiratory air trapping, bronchiectasis, or centrilobular nodules. Asthma, cystic fibrosis, bronchiectasis from another cause, recurrent infection, foreign-body aspiration, and other obstructive disorders must be excluded by the specialist team. Treatment is not an attempt to reopen scarred bronchioles. Supportive measures protect the remaining lung function: avoid further inhalational injury, maintain recommended vaccination, use respiratory...