Catamenial pneumothorax with bullae

The physiologic mechanisms and diagnostic approach of catamenial pneumothorax remain controversial. We report 3 patients with catamenial pneumothorax with bullae. Endometrial cells in these patients were located around the bullae, suggesting a possible new mechanism for catamenial pneumothorax in which cyclic endometrial shedding in the lung causes destruction of the lining of alveolar epithelial cells and forms bullae. Because intrathoracic endometriosis is considered an underrecognized cause of secondary spontaneous pneumothorax, we performed careful histologic examination for definitive diagnosis of thoracic endometriosis.