Background: Plastic bronchitis (PB) is a rare but potentially life-threatening condition, characterised by the formation of fibrinous casts in the trachea or bronchial tree. In the paediatric population, it most commonly affects children with congenital heart disease who have undergone cardiothoracic surgery, such as the Fontan circulation.However, it may also occur in association with infections, asthma, or other inflammatory conditions. Despite its severity, its pathophysiology remains poorly understood, presenting significant challenges for both diagnosis and management.Case Presentation Summary: A 12-year-old boy, with a prenatal diagnosis of aortic coarctation surgically corrected on the 4th day of life, presented to the emergency department following an episode of oxygen desaturation (SpO₂ 80–85%) triggered by coughing and the expectoration of a mucofibrinous, branched structure measuring approximately 6 cm, which his mother brought with her (Figure 1).The patient reported a one-week history of productive cough, without fever or other systemic symptoms, and occasional respiratory effort. On examination, he was eupnoeic, with SpO₂ of 99% on room air. Pulmonary auscultation revealed reduced breath sounds at the left lung base and occasional wheezing. Chest radiography showed opacification of the lower half of the left hemithorax, with marked delineation of the bronchial tree suggestive of fibrinous casts.During observation, the patient remained clinically stable, presenting productive cough, but did not expectorate additional casts. Peripheral oxygen saturation remained adequate on room air, and urgent bronchoscopy was therefore considered unnecessary. He was discharged home with mucolytic therapy and arranged for urgent follow-up in the Paediatric Pulmonology clinic.Learning points discussion: Although PB is rare in children, it should be considered in cases of airway obstruction, particularly in those with a history of congenital heart disease and prior cardiothoracic surgery. This condition results in the formation of fibrin-rich casts that may obstruct distal and intermediate airways, leading to hypoxaemia, respiratory distress, and, in severe cases, acute respiratory failure.The pathophysiology of PB remains poorly understood and is likely multifactorial, involving lymphatic dysfunction and inflammation. Diagnosis relies on clinical suspicion, imaging findings, and, when necessary, bronchoscopic visualisation and removal of casts.Management strategies include corticosteroids, mucolytic therapy and, occasionally, interventions targeting lymphatic drainage. Early recognition and appropriate follow-up are critical to prevent recurrence and reduce morbidity.Conclusion: Plastic bronchitis, though uncommon, is a serious condition in the paediatric population, particularly among children with a history of congenital heart disease surgery. Prompt recognition, supportive management, and multidisciplinary follow-up are essential to optimise outcomes and prevent life-threatening complications.
