Spontaneous chylopericardium in an adult due to mediastinal cystic hygroma

Chylopericardium is a rare and benign condition. Apart from common causes like non-surgical trauma, tuberculosis, malignancy, radiation, and postoperative, mediastinal cystic hygroma presenting as chylopericardium is an extremely rare entity. Primary or idiopathic chylopericardium is diagnosed when the precise cause is not known. It is a diagnosis of exclusion. We report a 27-year-old lady with mediastinal cystic hygroma, presenting as spontaneous chylopericardium, who was managed surgically with no recurrence on 18 months follow-up. She was evaluated for complaints of discomfort in the upper abdomen region and breathing difficulty in left lateral position for 4 days, and was found to have a large pericardial effusion with impending tamponade. She underwent pericardiocentesis, and on fluid analysis, it was confirmed as chylous pericardial effusion. She was evaluated thoroughly and was taken up for right video-assisted thoracoscopy. The thoracic duct was clipped and a window was created in the pericardium, the cystic hygroma was excised, and pleurodesis was done. The postoperative period was uneventful. Histopathology of the pericardial window showed chronic inflammatory pathology and cystic lesion was confirmed as a chylous cyst.