Catamenial pneumothorax

Onset of lung collapse is less than 72 hours after menstruation. Typically, it occurs in women aged 30 to 40 years, but it has been diagnosed in young girls as early as 10 years of age and post menopausal women (exclusively in women of menstrual age), most with a history of pelvic endometriosis.

Endometrial tissue attaches within the thoracic cavity, forming chocolate-like cysts. Generally the parietal pleura is involved, but the lung itself, the visceral layer, the diaphragm, and more rarely the tracheobronchial tree may also be afflicted.[2] The mechanism through which endometrial tissue reaches the thorax remains unclear. Defects in the diaphragm, which are found often in affected individuals, could provide an entry path,[3] as could microembolization through pelvic veins.[4]

The cysts can release blood; the endometrial cyst "menstruates" in the lung. Air can move in by an unknown mechanism. The blood and air cause the lung to collapse (i.e. catamenial hemopneumothorax).[5]

Diagnosis can be hinted by high recurrence rates of lung collapse in a woman of reproductive age with endometriosis. CA-125 is elevated. Video-assisted thoracoscopy is used for confirmation.

Pneumothorax can be a medical emergency, as it can become associated with decreased lung function, and if progressed to tension pneumothorax, potentially fatal. In many cases, catamenial pneumothorax will resolve spontaneously and not require immediate intervention. In more severe cases, a chest tube may be required to release air and/or blood and to allow the lung to re-expand.

Surgery, hormonal treatments and combined approaches have all been proposed, with variable results in terms of short and long term outcome.[7] Surgical removal of the endometrial tissue should be endeavoured during menstruation for optimal visualisation of the cyst.[8] Pleurodesis may also be helpful. Menstruation and accompanying lung collapse can be suppressed with hormone therapy,[9] like with Lupron Depot, danazol or extended cycle combined oral contraceptive pills, or GnRH antagonist medications.

Some sources claim this entity represents 3 to 6% of pneumothorax in women.[9] In regard of the low incidence of primary spontaneous pneumothorax (i.e. not due to surgical trauma etc.) in women (about 1/100'000/year),[9] this is a very rare condition. Hence, many basic textbooks do not mention it, and many doctors have never heard of it. Therefore, catamenial pneumothorax is probably under-recognized.[3]