Trauma-induced "Macklin effect" with pneumothorax and large pneumomediastinum, disguised by allergy.

A 56-year-old man presented spontaneously to the Emergency Department complaining of facial and neck oedema after assumption of nonsteroidal anti-inflammatory drugs (NSAIDS). The triage nurse assigned the patient to Accident & Emergency (A&E) doctor as probable allergic reaction to NSAIDS. Chest X-ray (CXR), ordered after 24 hours, revealed a huge subcutaneous chest and neck emphysema without clearly visible pneumothorax. Subsequent chest CT scan showed a small left pneumothorax and a large amount of air in the mediastinum. The patient was conservatively treated since he was eupnoeic and hemodynamically stable. The pathophysiology of pneumomediastinum was first described by Macklin in 1939. The Macklin effect involves alveolar ruptures with air dissection along bronchovascular sheaths to the mediastinum. In this case the patient did not report in his history a recent blunt thoracic trauma and the initial suspicion of an allergic reaction has prevented physicians to immediately achieve the correct diagnosis.