(1154) Cat’s out of the Bag: Catamenial Pneumothorax as Primary Manifestation of Endometriosis

Introduction: Endometriosis is an uncommon pathology with a prevalence of 5% among women aged 15-49 years. This disease is defined as the presence of endometrial tissue – glands and stroma – in an extrauterine space. This most commonly occurs in the pelvic compartment, manifesting as dysmenorrhea and affecting fertility. A rare presentation of endometriosis is thoracic endometriosis, and the most common clinical manifestation is catamenial pneumothorax. Both surgical and medical approaches are used in treatment. Here, we present a case of a 39-year-old female who presented to the emergency department with chest pain and dyspnea, found to have endometriosis, which only first manifested as a catamenial pneumothorax.

Description: A 39-year-old female, previously healthy, presented to the emergency department for progressively worsening shortness of breath for 10 days. The workup revealed a spontaneous right pneumothorax; she underwent a needle decompression but symptoms returned 3 days later. A chest tube was placed, but her pneumothorax recurred after chest tube removal. She underwent VATS with repair of a diaphragmatic defect and bleb removal. Pathology was negative for any endometrial stroma. On clinic follow-up a month later, her pneumothorax had recurred, coinciding with her first day of menses. She underwent repeat VATS with partial pleurectomy and mechanical pleurodesis, and was formally diagnosed with endometriosis. Despite initiation of OCPs, she continued to have recurrent pneumothorax, eventually requiring placement of an endobronchial valve. With continued OCP use, her recurrent pneumothorax resolved.

Discussion: The pathophysiology of endometriosis is not well understood; one prevailing theory is that cells are implanted in the peritoneal cavity via retrograde menstruation. In rarer cases, cells can transfer into the pleural space through microscopic or macroscopic defects in the diaphragm. A comprehensive history demonstrating temporal synchronicity with menses can help support a differential, a definitive diagnosis is made through pleural visualization and histologic analysis of pleural tissue. Hormonal therapy in adjunct with surgical management can help limit recurrence. In our case, despite multiple procedures, it was only after the addition of OCPs that symptoms failed to recur.