Background: Chylopericardium is a rare entity characterized by the accumulation of chylous fluid in the pericardial cavity. Lymphangioleiomyomatosis (LAM) is a rare, progressive systemic disease with prominent features of lung cysts, abdominal tumors, and the development of chylous effusions, usually in the thorax and/or abdomen. Chylopericardium in association with LAM is exceedingly rare, with only a few cases reported in the literature. Case Presentation: We report a case of a 61-year-old woman with chronic dyspnea and bilateral cystic lung disease who presented with a 1-week history of acutely worsening dyspnea. At presentation, she was tachycardiac and hypoxemic, an electrocardiogram detected sinus tachycardia, and a chest radiograph was indeterminate for a small right apical pneumothorax or an apical bulla. An urgent echocardiogram revealed a large pericardial effusion with features of cardiac tamponade, necessitating urgent pericardiocentesis. Analysis of the pericardial fluid confirmed the presence of chylopericardium and a diagnosis of LAM was made. Oral Sirolimus was started and at 1 year of follow-up, the patient has successfully avoided repeat pericardiocentesis. Conclusion: This case describes a rare presentation of a rare disease and suggests that treatment with sirolimus may potentially be effective in reducing the accumulation of chylopericardium in LAM.

Keywords: Lymphangioleiomyomatosis, lung cysts, cardiac tamponade, chylopericardium, dyspnea, case report.