Spontaneous pneumomediastinum has been described in patients with connective tissue disorders, along with interstitial lung diseases, including dermatomyositis and rheumatoid arthritis.4 5
Two cases of spontaneous pneumomdiastinum and concomitant pneumothoraces have been described with SLE and idiopathic interstitial pneumonia.6 7
However, both patients died as a result of their illness. Our patient did not have a pneumothorax, and the pneumomediastinum resolved completely in 5 days. Another patient with spontaneous pneumomediastinum but without idiopathic interstitial pneumonia has been described with SLE.8
These cases highlight a spectrum of presentations and varying prognosis of this condition.
In interstitial lung disease, the alveolar rupture that causes pneumomediastinum is thought to result from interstitial fibrosis, or pulmonary infarction caused by pulmonary vasculitis which is often a feature of connective tissue disorders.5
Respiratory tract infection has been described as a possible precipitating factor in some cases.1 5
In our patient, however, there was no clear precipitating factor.
Spontanous pneumomediastinum is usually self-limited, but a prolonged course going beyond 2 months and only responding to treatment with high-concentration oxygen has been described.5
Although no specific treatment for pneumomediastinum has been suggested in a published series,1
we treated our patient with high-concentration oxygen to expedite recovery. High-concentration oxygen has been recommended as treatment for pneumothorax and has been helpful for subcutaneous and mediastinal emphysema. Pneumothorax, subcutneous and mediastinal emphysema is reabsorbed into capillaries by diffusion along a partial pressure gradient caused by the sum of partial pressures exerted by water, carbon dioxide, nitrogen and oxygen. With breathing 100% oxygen, nitrogen is washed out of the blood, thus increasing the gradient for gas absorption and causing a four- to six-fold increase in the rate of gas absorption.9 10
We assume that the speedy recovery of pneumomediastinum and subcutaneous emphysema in our patient may have resulted from treatment with high-concentration oxygen; but, in the absence of a case–control study, we cannot be certain, as most cases recover spontaneously.1
- Spontaneous pneumomediastinum is a rare complication of idiopathic interstitial pneumonia associated with SLE that results from the rupture of alveoli adjacent to the mediastinum.
- The chest radiological signs depend on delineation of the normal anatomical structures that are outlined by air within the mediastinal planes.
- The extrathoracic physical and radiological findings in pneumomediastinum can be explained by air tracking along anatomical communications between mediastinal tissue planes and structures outside the chest.
- Spontaneous pneumomediastinum is usually self-limited, but treatment with high-concentration oxygen expedites air absorption from the mediastinum and subcutaneous tissues and speeds up recovery.