Gorham-Stout syndrome, also called "disappearing bone disease, diffuse cystic angiomatosis of bone, disseminated lymphangiomatosis, Gorham's vanishing bone disease, phantom bone disease or idiopathic massive osteolysis, is a rare disease of unknown etiology and pathogenesis. It is characterized by rapidly progressive localized massive osteolysis associated with proliferation of vascular structures of benign origin in which the absence of new bone formation is representative. When it is complicated by chylothorax, the prognosis is poor. The authors report a 6-year-old boy with Gorham-Stout syndrome who presented with pleural effusion showing features of chylothorax, who responsed poorly to currently available therapeutic modalities.