Bronchiolitis Obliterans (Pediatrics)

Bronchiolitis obliterans (BO) is a chronic, largely fixed small-airway disease. It is not acute viral bronchiolitis. Acute viral bronchiolitis is a self-limiting viral lower respiratory tract infection of generally healthy children up to 24 months of age. It typically presents with a first episode of wheezing before 12 months of age, it tends to worsen over the first 72 hours, and it is managed with supportive care: hydration, minimal handling, gentle nasal suctioning and oxygen when saturation falls below 90%. BO is what a small number of children are left with after a severe lower respiratory infection, or after a transplant, when the bronchioles heal with scar instead of normal lining. The mechanism explains the bedside picture. An injury to the bronchiolar epithelium triggers inflammation and then progressive fibrosis of the small airways, producing uneven narrowing or complete obliteration of the lumen. Scarred bronchioles cannot reopen, so the obstruction is fixed, air becomes trapped behind the narrowed airways, and symptoms persist or recur rather than settling in days. Initial mild symptoms do not exclude persistent breathlessness as the disease progresses....