With regard to the question we pose in the title, we would like to comment on spontaneous pneumomediastinum (SPM).

We have read with great interest the recently published Letter to the Editor, “A Child With Severe Pneumomediastinum and ABCA3 Gene Mutation: A Puzzling Connection”.1 We are interested in the relationship described between mutations of the ABCA3 gene and certain pulmonary pathologies associated with alterations in the surfactant. However, we disagree with the transcendental role that the authors attribute to SPM and its status of severity, which we believe to be inaccurate. Furthermore, we believe that what should be explored is the relationship between these genetic alterations and the pulmonary pathology that leads to the SPM, as the latter is just a consequence (presence of air in the mediastinum with no known cause).

SPM is a rare pathology in children and adults.2,3 It is observed as a consequence of an increase in intra-alveolar pressure, alveolar rupture and migration of the air dissecting the peribronchial and perivascular sheaths of the pulmonary hilum, extending to the mediastinum.2–5 This, at the same time, can propagate towards the subcutaneous, endothoracic and peritoneal tissue, and even to the spinal canal. This mechanism is also known as the “Macklin effect”, as Macklin was able to demonstrate this experimentally in 1937 by inflating the bronchi of cats. A few years later, Hamman made the first clinical report.4

Predisposing conditions that have been described include asthma, interstitial pulmonary diseases, COPD, bronchiectasis, lung cysts and lung cancer, among others. An increase in intra-alveolar pressure produced, for example, during vomiting, the inhalation of toxins, intense cough, physical exercise or childbirth, together with bronchopulmonary infections or the ingestion of a foreign body, may trigger an SPM.5 The patient who was reported had presented acute respiratory infection associated with cough.1

SPM is considered a process with little clinical impact and a good prognosis.2–5 It requires no more than oxygen therapy, analgesia, follow-up and treatment of the underlying cause, after which it completely resolves in a matter of a few days. Poor patient evolution is usually caused by the associated underlying lung disease. Tension pneumothorax and pneumopericardium are the exceptions: these should be considered severe and required specific treatment (emergency drainage).3,6

In our setting, pneumomediastinum and later subcutaneous emphysema are often a cause for panic in patients, family members and even some health-care staff, which may sometimes lead to inappropriate behavior and treatment. We therefore believe that it is important to clarify the true meaning of SPM.