Capillary leak syndrome in neuromyelitis optica treated with rituximab

61-year-old woman with Neuromyelitis optica (NMO) diagnosis treated with rituximab was referred to our hospital with severe hypovolemic shock and anasarca. The laboratory findings showed marked hemoconcentration and a decrease in total serum protein. She developed a multiple organ failure and died three hours later. We diagnosed the patient as having capillary leak syndrome (CLS). CLS is a very rare condition caused by unexplained episodic capillary hyperpermeability, which can be idiopathic or secondary to some conditions like infection, malignant disease and some drugs like monoclonal antibodies. We reported the first CLS case in NMO patient treated with rituximab.