What are the potential causes?
In the absence of trauma, causes include tall physique, asthma, ruptured apical bleb or Marfan syndrome (or other connective tissue disorders).
With that differential in mind, is the cause demonstrated?
The surface of the apical portion of the right lung is irregular and the suspicion is that this represents an apical bleb.
How would you confirm this?
Chest CT would be the best way to confirm the diagnosis.
Right simple pneumothorax.