Unmasking the Macklin effect: A rare case of coexisting pneumothorax and pneumomediastinum triggered by the Macklin effect

Dear Editor,

We would like to congratulate and thank Dr Joses Dany James and the coauthors for their interesting article published online in December 2025 in the journal. We read the article “Pneumoperitoneum in the absence of intestinal injury in blunt thoracic and abdominal trauma: A case series with review of literature”¹ with great interest. The authors should be commended for highlighting an important diagnostic dilemma in trauma care and for emphasizing that pneumoperitoneum following blunt trauma does not invariably indicate hollow viscus perforation or mandate operative intervention.

While the article primarily focuses on pneumoperitoneum without hollow viscus injury, we would like to add to this discussion by emphasizing that Pneumomediastinum after blunt chest trauma also often raises concern for an underlying aerodigestive tract injury and may prompt an extensive diagnostic workup. However, in some stable patients, pneumomediastinum results from the same mechanism known as the Macklin effect.² The Macklin effect involves alveolar rupture with air dissecting along the bronchovascular sheaths into the mediastinum. We report a case that highlights the Macklin effect in pneumothorax and pneumomediastinum following blunt chest trauma and supports a conservative management approach.

A 27-year-old male presented to our Emergency Department within one hour of the road traffic accident involving a bike skid. On initial assessment, he was hemodynamically stable. Physical examination revealed right-sided thoracic subcutaneous emphysema and a positive chest compression test on the right. Chest radiography demonstrated a right-sided pneumothorax with associated subcutaneous emphysema and pneumomediastinum, without evidence of rib fractures [Figure 1a]. A right intercostal tube drain was inserted. Contrast-enhanced computed tomography of the torso confirmed right-sided pneumothorax with the chest tube in situ, pneumomediastinum, and subcutaneous emphysema extending into the neck and right chest wall, with no evidence of aerodigestive or vascular injury [Figure 1b]. The patient was admitted for observation and managed conservatively with analgesia, incentive spirometry, and chest physiotherapy. His clinical condition improved progressively, with complete resolution of the subcutaneous emphysema. The intercostal tube drain was removed on the fourth post-injury day, following radiographic confirmation of complete lung expansion [Figure 1c], and the patient was discharged in a stable condition. He remains asymptomatic on outpatient follow-up.

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Figure 1:

(a) Initial chest X-ray showing right pneumothorax (white arrow), subcutaneous emphysema (black arrow), and pneumomediastinum (red arrow). (b) CT Chest demonstrating right subcutaneous emphysema (yellow arrow), pneumothorax (white arrow) with an intercostal tube drain, and pneumomediastinum (red arrow). (c) Chest X-ray after drain removal, showing fully expanded lungs.

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Traumatic pneumomediastinum occurs in up to 10% of blunt chest trauma cases.³ Although pneumomediastinum and subcutaneous emphysema following severe blunt thoracic or cervical trauma are often considered indicators of serious aerodigestive injury, a major aerodigestive tract injury is found in only about 7% of these patients.⁴ The pathophysiological mechanism of pneumomediastinum was first described by Macklin in 1939.² Following chest trauma, air escapes from the alveoli, enters the interstitial tissue of the lung, and travels along the pulmonary vessels and fascial planes to the lung root and subsequently into the mediastinum. Treatment of subcutaneous emphysema focuses on addressing the underlying cause. Pneumomediastinum often resolves spontaneously with rest and observation. However, some patients may develop tension pneumopericardium, leading to cardiac tamponade without any free fluid in the pericardial space.⁵ In such cases, an emergent pericardial aspiration followed by the creation of a subxiphoid pericardial window is a life-saving procedure.

This case reinforces that hemodynamically stable trauma patients with pneumothorax and pneumomediastinum following blunt chest trauma, in the absence of clinical or radiological evidence of aerodigestive injury, can be safely managed with conservative treatment and observation.