Catamenial pneumothorax is an abnormal build-up of air/gas in the pleural space between the lung and the chest wall - specifically within 72 hours before or after the onset of a menstrual cycle. It was first described in 1958.

It generally leads to chest pain, shortness of breath, and coughing.

It's believed to be related to Endometriosisplugin-autotooltip__plain plugin-autotooltip_bigEndometriosis

"Endometriosis is a condition in which cells similar to those in the endometrium, the layer of tissue that normally covers the inside of the uterus, grow outside the uterus. Most often this is on the ovaries, fallopian tubes, and tissue around the uterus and ovaries; however, in rare cases it may also occur in other parts of the body.", but exact details regarding its cause are currently unknown. In addition, it's thought to be largely undiagnosed or misdiagnosed, thus, though seemingly rare, its true prevalence in the general population is also considered unknown.

Many questions remain unanswered regarding the pathogenesis of catamenial pneumothorax. Various mechanisms may contribute in individual patients, and further investigations are needed. Because of the rarity of this condition, no randomized or controlled trials are available to guide the therapy for women with catamenial pneumothorax."

Source (with further details) : Mayo Clinic Proceedings Volume 80, Issue 5, pp 677-680