Spontaneous pneumomediastinum diagnosed by the Macklin effect

Vomiting-induced pneumomediastinum is often caused by oesophageal perforation or alveolar rupture due to increased pressure. A correct diagnosis is important because both diseases have different treatments and severities. We report the case of a 21-year-old man who presented with chest pain and fever after frequent vomiting and had elevated white blood cell counts on blood tests. There was extensive pneumomediastinum, and the lower oesophagus was swollen and thickened on chest computed tomography. An oesophagram was not possible due to severe nausea and vomiting. Accumulation of free air was found along the peripheral bronchi or the pulmonary vascular sheath in the left lower lobe, which was continuous with the mediastinum. Based on the presence of the Macklin effect, we diagnosed a pneumomediastinum with a high possibility of spontaneous pneumomediastinum. The Macklin effect is a finding that can likely distinguish oesophageal perforation from spontaneous pneumomediastinum.