A 25-year-old woman presented to our hospital with a 1-week history of cough and 
shortness of breath. A chest radiograph showed a left-sided pleural effusion that contained chyle. The findings of other examinations suggested no distinct disease. We made the diagnosis of idiopathic chylothorax and operated only on the left side because magnetic resonance thoracic ductography depicted the thoracic duct on the left side. The intraoperative finding was chylous effusion flowing through a pleural fistula over a cystic lesion. We resected the lesion and ligated the thoracic duct in a left thoracotomy. The histopathologic diagnosis was Lymph Angioleio Myomatosis (LAM), which recurred after the operation. Sirolimus was given along with redo ligation of thoracic duct, resulting in cessation of chylothorax. A preoperative evaluation on possible LAM might have prevented 
the recurrence in combination with sirolimus.