A skinfold may be mistaken for pneumothorax, but there are differences. A pneumothorax must conform to the shape of the pleura (it won't extend outside the chest or to the contralateral side), contains only air (it will be black with no lung markings), and is a thin white line (skinfolds tend to be thicker lines). In this case, the skinfold line extends from the right hemithorax to the left hemithorax, there are lung markings beyond the skinfold line and the skinfold line is thicker than the pencil-thin pleura. If you look carefully, you can even see a second skinfold.