Skin fold mimicking pneumothorax

Case contributed by Dr Andrew Dixon


Shortness of breath.

Patient Data

Age: 90 years
Gender: Male

There is a curvilinear well-defined edge projected over the lateral aspect of the left lung paralleling the chest wall. Additionally, there are linear lucencies projected in the soft-tissues at the left and right inferior lateral chest walls. On first inspection, the appearance is very convincing for a left-sided pneumothorax and associated small volume subcutaneous emphysema. However, on close inspection, it is noted that vascular markings do extend beyond what would be the pleural margin (best seen on sharp algorithm) and the would-be pleural margin is not a thin white line but is instead a 1 cm thick white line that fades medially and abruptly stops laterally. The appearance is therefore that of a skin fold which is mimicking a pneumothorax, and additional skin folds mimicking subcutaneous emphysema. 

Initial x-ray was misinterpreted as being a left pneumothorax and a CT was ordered to look for a cause of spontaneous pneumothorax. The CT reveals no pneumothorax but does nicely demonstrate the multiple skin folds which have created the artefact on the x-ray. 

Case Discussion

This case strikingly demonstrates how skin folds can mimic pneumothorax on AP chest radiographs, particularly in older patients. This issue tends not to occur with PA chest radiographs as in that case the patient's back is not pressed against anything and the hugging of the detector plate by the patient helps to stretch out any lax skin.

It is worth being aware of this potential pneumothorax mimic and noting that instead of the edge being a thin white line, a skin fold is always seen as a thick white line that fades in on one side and abruptly stops on the other side. Also, one can usually see vascular markings extending beyond the edge of a skin fold, whereas vessels would be completely absent in pneumothorax. Clinical assessment (auscultation and percussion) and ultrasound (to look for sliding lung sign) can be very useful to prevent a chest tube being needlessly inserted in cases such as this. 

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