Catamenial pneumothorax

Catamenial pneumothorax is a spontaneous pneumothorax that recurs during menstruation, within 72 hours before or after the onset of a cycle. It usually involves the right side of the chest and right lung, and is associated with thoracic endometriosis. A third to a half of patients have pelvic endometriosis as well. Despite this association, CP is still considered to be misunderstood as is endometriosis considered to be underdiagnosed. The lack of a clear cause means that diagnosis and treatment is difficult. The disease is believed to be largely undiagnosed or misdiagnosed, leaving the true frequency unknown in the general population. Catamenial pneumothorax is defined as at least two episodes of recurrent pneumothorax corresponding with menstruation. It was first described in 1958 when a woman presented with 12 episodes of right sided pneumothorax over 1 year, recurring monthly with menstruation. Thoracotomy revealed thoracic endometriosis. Many patients present with chest pain close to their menstrual periods. Surgical exploration can be used in an attempt to visualize the problem; mechanical pleurodesis or hormonal suppressive therapy can also be used. Thoracic endometriosis is the most common non abdominal site of involvement and is also the primary risk factor for catamenial pneumothorax. Catamenial pneumothorax is the primary clinical presentation of thoracic endometriosis, and is defined as recurrent episodes of lung collapse within 72 hours before or after menstruation.

Symptoms include chest or shoulder pain, cough, dyspnea, and shortness of breath. Chest and shoulder pain can be radiating out to the shoulder blades. A dry cough can also present and come with a "crackling" sound upon inhaling. Chest pain requires immediate medical attention.

Although the exact cause is not known, a few theories come from metastatic, hormonal, and anatomical possibilities. The metastatic model proposes that endometrial tissue has migrated from the endometrium to the diaphragm or the pleural space, causing small holes in the diaphragm, allowing air into the pleural space. In the hormonal model, it is believed that prostaglandin F2 causes a narrowing of the bronchioles, the small tubes within the lungs. Narrowing of these can cause the alveoli to rupture which may trap air in the pleural space. In the anatomical model, researchers believe that the absence of the cervical mucous plug, which is normally there during the menstrual cycle, allows air to pass from the genital tract to the pleural space through fenestrations in the diaphragm. Another theory is that hormonal changes that come with the menstrual cycle can cause blebs to spontaneously rupture. Blebs are small blisters/pustules filled with air or fluid and can develop on the lungs. Peritoneal flow occurs in a clockwise pattern, which could likely explain the tendency for catamenial pneumothoraces to be right sided. Defects in the diaphragm, which are found often in affected individuals, could provide an entry path, as could microembolization through pelvic veins. Such diaphragmatic defects may be either congenital or acquired. The cysts can release blood; the endometrial cyst "menstruates" in the lung. Endometrial cells undergo structural changes during the secretory phase of the menstrual cycle, in a process called decidualization. Decidualized pleural endometrial implants can disrupt the pleura and lead to pneumothorax (and hemothorax).

Diagnosis can be hinted by high recurrence rates of lung collapse in a woman of reproductive age with endometriosis. CA 125 is elevated. Clinical diagnosis can be made based on history and imaging, while the gold standard for definitive diagnosis remains Video assisted thoracoscopic surgery, or VATS, which allows not only the visualization of the lesion, but also surgical treatment via cauterization of the ectopic endometrial tissue. Special staining under a microscope or utilizing a cell marker, such as PAX8, can be used to positively identify endometrial stroma.

Pneumothorax can be a medical emergency, as it can become associated with decreased lung function, and if progressed to tension pneumothorax, potentially fatal. In many cases, catamenial pneumothorax will resolve spontaneously and not require immediate intervention. In more severe cases, a chest tube may be required to release air and/or blood and to allow the lung to re expand. Surgery, hormonal treatments and combined approaches have all been proposed, with variable results in terms of short and long term outcome. These have both been effective, separately and together. Both have been used to treat women with this condition, and specifics depend on each patient and each situation. Surgery may be used to excise endometrial tissue from the lungs and pleural space as well as repair damage and holes in the diaphragm. Pleurodesis may also be effective in removing the space between the lung and the chest wall; preventing air build up between these layers. Non surgical treatment includes pharmacological treatment via continuous oral contraceptive therapy to avoid cyclical bleeding with monthly menstruation. Oral contraceptives appear to be preferable for patients due to fewer negative side effects than treatment with GnRH agonist therapy, which can lead to hypoestrogenic effects including osteoporosis, resulting in discontinuation of therapy and thus a higher likelihood of recurrence of catamenial pneumothorax. In regard of the low incidence of primary spontaneous pneumothorax (i. e. not due to surgical trauma etc.) in women (about 1/100'000/year),