Haemoptysis following shallow breath-hold diving in a cannabis user.

We report the first case of a healthy 24-year-old male with a 6-year history of regular cannabis use, who presented with haemoptysis after a shallow 3 m breath-hold dive. Blood investigations showed mild neutrophilia. CT thorax revealed focal ground-glass changes in the superior segment of the lower lobe. With a suspicion of pneumonia, oral antibiotics were initiated to poor effect. Through bronchoscopic visualisation and lavage, a diagnosis of diffuse alveolar haemorrhage was established. The clinical course was benign with resolution of symptoms and changes on CT thorax within 6 weeks of stopping marijuana use. Since all other causes of haemoptysis were excluded, pathophysiology was attributed to cannabis-induced lung parenchymal damage, exacerbated by a shallow breath-hold dive. To ensure appropriate management, a clinician should therefore have a high index of suspicion for drug use and other factors known to cause chronic lung damage in whom other causes of diffuse alveolar haemorrhage are excluded. © BMJ Publishing Group Limited 2020. No commercial re-use. See rights and permissions. Published by BMJ.