Perspective on the etiology of catamenial pneumothorax

Background: Catamenial pneumothorax (CP) is a relatively rare disease, which is a form of a recurring pneumothorax in women of reproductive age. The actual cause is still unclear. Objectives: To perform histopathologic evaluation of the etiology of CP. Methods: We retrospectively reviewed intraoperative findings and pathological specimens of women with pneumothorax who underwent surgery from January 2014 to December 2019. Five patients were suspected with CP based on the clinical history, and computed tomography images showed no bullae. In the other 13 patients, bullae, which seemed to be the culprit lesion, were detected before or during surgery. Results: All patients with suspected CP had diaphragmatic holes, also known as “blue berry spots.” Pathologically, these lesions had endometrial tissue (ET). Diaphragmatic repair was performed for four patients, one of whom developed recurrent pneumothorax and bullae with ET, as identified at reoperation. Another patient had a brown lesion in the right lower lung lobe (Figure 1-a). Its histopathology showed subpleural ET (Figure 1-b, 1-c). The bullae of the other 13 women did not contain similar tissue. Conclusions: Diaphragmatic lesions are considered to cause CP, but this may not always be the case. We hypothesized that ET spreads in the peripheral lung tissue and that air leakage occurs through such lesions at the time of menstruation in cases of CP.