Pneumomediastinum and subcutaneous emphysema after high pressure air and sand injection injury to the upper arm

We present a rare case of a 47-year-old man who developed pneumomediastinum and subcutaneous emphysema after a high pressure hose accidentally injected air and sand particles into his right upper arm. On presentation, he complained of dyspnoea and chest pain. He had palpable subcutaneous emphysema extending from the upper arm to his neck, face, and trunk. Plain X-ray films and computed tomography showed pneumomediastinum and subcutaneous emphysema, but no sand particles. Conservative treatment was done with close observation, and serial radiographs were obtained. There was complete resolution of the mediastinal and subcutaneous air after about two weeks with no evidence of infection. This was an extremely rare case of pneumomediastinum and severe subcutaneous emphysema occurring after accidental air injection injury to the upper arm. With regard to how air entered the mediastinal cavity, possible pathways are discussed.