We report a case of a 20-year-old white woman with the history of anorexia nervosa presenting with spontaneous pneumomediastinum (SPM). On admission, her body mass index (BMI) was 9.9 kg/m2. Physical examination revealed subcutaneous crepitation especially in the axillae, the intercostal spaces, between the scapulae and along the spine. A chest X-ray showed extensive tissue emphysema, especially in the upper mediastinum. In a computed tomography (CT) scan, additional air was found in the upper retroperitoneal space adjacent to the stomach and to the left of the aorta. The patient recovered clinically within three weeks, and a CT scan showed a complete remission of the pneumomediastinum and subcutaneous emphysema. Based on this, case review of the literature about the frequency of pneumomediastinum in young patients with low weight is presented concerning epidemiology, etiology, symptoms, diagnosis, treatment, time to recovery and prognosis. Copyright © 2010 John Wiley & Sons, Ltd and Eating Disorders Association.