A very rare entity: catamenial pneumothorax.

Catamenial pneumothorax, a variant of spontaneous pneumothorax occurs exclusively in women of menstrual age. Catamenial pneumothorax is associated with a high rate of recurrence. The etiology and pathogenesis is enigmatic. We describe the case of a 42-year-old woman with right-sided catamenial pneumothorax recurring four times, caused by ectopic endometriosis in the pleural layers which was confirmed histopathologically. Surgical treatment should be accomplished during menstruation for optimal visualization of pleurodiaphragmatic endometriosis.