antiaquaporin4 antibodypositive optic neuritis treated with doublefiltration plasmapheresis purpose the antiaquaporin4 aqp4 antibody was recently reported to be associated with neuromyelitis optica nmo optic nerve involvements in many nmo cases are bilateral and the prognosis is poor however it has been suggested that plasma exchange is effective for those patients when steroid pulse therapy is ineffective herein we report successful treatment of a patient with nmo using doublefiltration plasmapheresis dfppcase a 22yearold woman consulted a neurologist for neck pain in march 2008 highintensity lesions were shown in the cervical spinal cord by t2weighted magnetic resonance imaging on july 15 the patient was referred to our department for a headache and pain and blurred vision in the left eye the bestcorrected visual acuity was 2050 and 20500 in the right and left eyes respectively with visual field defects observed in both after 3 courses of steroid pulse therapy antiaqp4 antibodies were positive in november the patient again noticed visual acuity loss in the left eye and was treated by additional steroid pulse therapy which was not effective next she underwent plasma exchange therapy though it was stopped due to hypotension and dyspnea the next day the patient underwent dfpp treatment and visual function gradually recoveredconclusion it is important to consider nmo when steroid pulse therapy is not effective we successfully and safely treated nmo in a young adult patient using dfpp