Catamenial pneumothorax in thoracic endometriosis syndrome

Dear Editor, Catamenial pneumothorax is defined as the pneumothorax occurring between one day prior to and upto 72 h after the onset of menstruation.[1] It is a relatively rare entity and requires a high index of clinical suspicion. Any reproductive age group woman developing pneumothorax without any apparent underlying lung disease should be considered for search of aetiology as catamenial pneumothorax. Most commonly presenting as right-sided pneumothorax can be left-sided or bilateral pneumothorax as a part of thoracic endometriosis syndrome (TES).[2] Endometriosis is the presence of ectopic endometrial tissues (functional glands and stroma) outside the normal uterine cavity. Common ectopic sites are pelvic organs followed by a thoracic cavity. Coelomic metaplasia, retrograde menstruation, endometrial tissue microembolism, clockwise peritoneal circulation, and transgenital-transdiaphragmatic movement of air are the common theories postulated for thoracic endometriosis.[3] Diagnosing thoracic endometriosis requires histological confirmation, whereas catamenial pneumothorax is a clinical diagnosis. Here, we present a case of thoracic endometriosis masquerading as recurrent ipsilateral pneumothorax and the role of medical thoracoscopy in its diagnosis. A 47-year-old hypertensive, diabetic, hypothyroid homemaker female presented with intermittent right-sided sharp chest pain and dyspnoea on exertion for the last 10 months. Pain was associated with pain in the tip of the right shoulder. Dyspnoea was of mMRC grade I, nonprogressive. She denied any history of cough, haemoptysis, fever or weight loss. Her past illness dates back to December 2022 when she had a similar episode of illness and evaluation revealed right-sided pleural effusion on chest X-ray. Diagnostic thoracentesis showed the fluid to be haemorrhagic. Biochemical and cytological analysis showed it to be exudative, lymphocytic in nature with raised adenosine deaminase (ADA). Antitubercular regimen was started on a clinic-radiological basis. Her menstrual history suggested the presence of dysmenorrhea. After three months of therapy, the patient required hospitalization due to nonresolving symptoms. This time repeat pleural fluid study confirmed the earlier findings except for ADA which was low. Papanicolaou stain (PAP) smear showed haemosiderin-laden macrophages; no malignant cells were found. Pleural fluid GeneXpert was negative. A pigtail catheter drain was inserted into the right hemithorax for symptomatic relief. 18FDG whole body positron emission tomography and computed tomography (PET CT) scan was done which showed non-fluoro deoxy glucose (FDG) avid septated cystic space occupying lesion (SOL) in the right adnexa 6.6 × 7.3 × 5.8 cm and in the left adnexa a cystic SOL of 3.6 × 3.2 cm. No other foci as the primary for pleural effusion was found. The patient was discharged after pigtail removal with an advice to continue antitubercular therapy. Later for dysmenorrhea, a transvaginal ultrasound showed the right adnexal cyst of the same size as seen in FDG PET. As a part of preoperative evaluation for pelvic surgery, a chest X-ray was done showing right-sided apical pneumothorax. Intercostal chest drain (ICD) was inserted and removed after lung expansion. Soon after removal, she started having similar symptoms and this time chest imaging showed ipsilateral pneumothorax [Image 1a] which persisted for months evident on serial chest X-rays. On careful elaboration of clinical history, it was found that patient had respiratory symptoms each time she had menstruation. A provisional diagnosis of catamenial pneumothorax was made. To establish the illness as a case of thoracic endometriosis, medical thoracoscopy was done. Visualized costal pleura showed multiple areas of “powder burn” appearance and a white nodule seen over the diaphragm [Image 2a]. Multiple visceral pleural blebs were seen. Pleural biopsies were taken from the powder burn appearances and sent for histopathological examination (HPE). Pleural fluid sent for packed cell volume (PCV) was more than 50% of the blood which clinched the diagnosis of catamenial haemo-pneumothorax. Postoperative period was uneventful, and pleurodesis was done 4-gm talc slurry after radiological complete lung expansion [Image 1b]. HPE revealed scattered polygonal cells in stroma with dense diffuse collection of haemosiderin laden macrophages [Image 2b]. Polygonal cells were positive for oestrogen and progesterone receptors confirming the diagnosis of pleural endometriosis and a diagnosis of TES was made. The patient was discharged after ICD removal and oral norethisterone was started.Image 1: (a) Right Pneumothorax. (b) Post pleurodesisImage 2: (a) Powder burn on costal pleura. (b) HistologyTES is considered to be progressive endometriosis disease supported by the higher age of onset and concomitant pelvic disease. Gold standard for diagnosing thoracic endometriosis is video-assisted thoracoscopic surgery (VATS) followed by histological examination although tissue sampling can have inconsistent result.[4] Immunohistochemical confirmation may be necessary as it happened in this case.[5] Yield can be increased if the sampling is done during active menstruation.[6] This case also points towards the utility of medical thoracoscopy in diagnosing TES obviating the need for VATS. which requires general anaesthesia and is associated with increased postoperative pain. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.