[Thoracic endometriosis: A difficult diagnosis]

Thoracic endometriosis is a rare disease, which presents in women at a mean age of 35 years, later than for pelvic endometriosis. There are no known predisposing factors for the condition and its pathogenesis is not yet clearly established. The symptoms always appear in connection with the periods of the person affected by the condition, occurring within 24-48 h after the start of menstruation. Catamenial pneumothorax is the most common clinical entity. It is associated with pelvic endometriosis in 30-50% of cases. Thoracoscopy, preferably performed during menstruation, allows full inspection of the diaphragm and the pleural cavity for defects in the diaphragm, endometrial nodules and bullae. The level of CA 125 is often elevated but this is not a reliable or specific marker. Medical treatment is aimed at blocking the action of estrogen on the endometrium and ectopic endometrial implants. GnRH analogues or danazol are the preferred treatments. Surgery to repair and strengthen the diaphragm and/or resect nodules or bullae also has a role, supplemented by pleurodesis to prevent further pneumothorax or effusions. The main risk is recurrence, and thus the current usual practice is to combine surgery, immediately followed by hormone therapy focusing on GnRH analogues.