Diaphragmatic fenestration identified in a patient with recurrent catamenial pneumothorax

Introduction: Catamenial pneumothorax is a rare entity first described in the late 1950s that is characterized by recurrent accumulation of air in the thoracic space during or preceding menstruation. The exact mechanism of this type of pneumothorax is unclear. Diaphragmatic fenestrations are visualized infrequently. We present a case in which a diaphragmatic interruption was clearly visualized during video-assisted thoracoscopy. Case Presentation: A 39-year-old female was referred to our institution for evaluation of recurrent episodes of right-sided pneumothoraces. She was in excellent health 12 years prior to presentation before developing episodes of chest discomfort characterized by a "dull ache" in the right anterosuperior chest. At first, the pain episodes resolved spontaneously. Gradually, however, the pain occurred more frequently and became associated with dyspnea and a sensation of a "fluid motion" in her chest. A small apical pneumothorax was identified radiographically after an episode of pain 10 years prior to presentation and she was noted to redevelop apical pneumothoraces several times each year, usually at the onset of menstruation. Although frequent, the pneumothoraces were never greater than 15% by volume and the patient had not previously undergone needle or chest tube decompression. Trial therapies with danazol, leuprolide, and medroxyprogesterone acetate were unsuccessful. Three weeks prior to presentation, the patient noted increasing dyspnea on exertion, then experienced right-sided neck pressure and progressive right-sided chest discomfort. She was referred to our institution where she was noted to have complete collapse of the right lung radiographically. Screening serologies, EKG, and arterial blood gas analysis were unremarkable. Chest tube decompression was initiated, followed by video-assisted thoracoscopic exploration of the right pleural cavity. A 1-cm circular diaphragmatic fenestration was identified (to be shown) and sutured closed followed by mechanical pleurodesis. No intrathoracic endometriosis was identified and no blebs or bullae were visualized. Post-operative recovery was uneventful and she has been free of symptoms since her procedure. A chest radiograph performed three months after the procedure was negative. Discussion: Although cases of spontaneous pneumothorax are relatively common, recurrent pneumothoraces associated with menstruation is rare. The term "catamenial" is derived from the Greek root meaning "monthly" and was first coined by Lillington and colleagues in 1972. Women in the third or fourth decade of life typically present with chest pain or dyspnea within 72 hours of the onset of menses. Catamenial pneumothoraces are usually unilateral and right-sided and multiple episodes often occur prior to diagnosis. Interestingly, clinical or pathological endometriosis is identified in only 22-37% of cases and diaphragmatic fenestrations are seen in only 19-33% of reported cases. The mechanism of catamenial pneumothoraces is unclear, but proposed etiologies include: the presence of subpleural blebs; extrusion of the cervical mucous plug that releases peritoneal air through congenital diaphragmatic defects or by endometrial implants causing focal defects; release of dinaprost tromethamine (prostaglandin F₂) in menstrual debris causing potent bronchiolar and vascular constriction, resulting in alveolar rupture; or swelling of intrapulmonary endometrial implants in response to perimenstrual hormonal changes creating a check-valve obstruction of terminal bronchioles. Conclusion: Catamenial pneumothoraces are an uncommon cause of spontaneous pneumothorax. Direct visualization of a diaphragmatic fenestration lends support for hypotheses involving diaphragmatic defects as possible avenues of air collection in the thorax.