Keywords: NMO; Ulcerative colitis; Aquaporin Case ReportA 35-year-old lady referred for recurrent bilateral severe optic neuritis. Her past medical history is significant for ulcerative colitis (UC) diagnosed in 2006 and treated successfully with azathioprine (AZA).In August 2010, one year after AZA discontinuation, she had her first attack of severe right optic neuritis that caused blindness for which she received 5-day-course of intravenous methylprednisolone (IVMP) with complete recovery. Three months later, she had similar attack that was treated with another course of IVMP but with partial improvement. In May 2012 she had another episode of simultaneous bilateral severe optic neuritis not responding to 2 courses of IVMP. The MRI showed the enhancement of both optic nerves, chiasm, optic tracts, and lateral geniculate bodies (Figure 1a and 1b).Upon presentation to our hospital 5 months after the last attack, she was blind and had no light perception. Her pupils were not reactive to light; she had pale optic discs, and otherwise normal neurological exam. A repeated MRI showed residual optic nerve atrophy with no brain or spinal cord lesions.Patient's serum sent for neuromyelitisoptica (NMO) antibodies in Mayo clinic laboratories were positive with a titer of >1:160, and the diagnosis of NMO spectrum disorder (NMOSD) was confirmed. Other serological investigations showed negative rheumatoid factor, ANA, anti-DNA, anti-Ra, anti-La antibodies. A spinal tap showed normal levels of protein, glucose, and cells; oligoclonal bands were absent.While the patient was scheduled to receive rituximab infusion, she had another relapse in December 2012 causing left sided weakness and hemianasthesia. The repeated MRI showed a "longitudinally extensive" lesion involving the right internal capsule and right cerebral peduncle (Figures 1b-1h). Her spine MRI was normal. She received 5-day-course IVMP with good recovery, followed by rituximab infusion of 1000 mg biweekly (Table 1).Six months after treatment, her neurological exam came back to baseline and she continued to receive rituximab 1000 mg biweekly every 6 months. She also remains in remission from her ulcerative colitis since 2006. DiscussionCoexistence between NMO and both organ-specific and nonorgan-specific systemic autoimmune diseases is not uncommon. In a cohort study of 153 patients with NMOSD, 4 (2.6 %)patients diagnosed with ulcerative colitis, 26 (17.0%) with autoimmune thyroid disease, 5 (3.2%) with systemic lupus erythematosus or sjogren's syndrome, 2 with idiopathic thrombocytopenic pupura (1.3%), 2 with rheumatoid arthritis (1.3%), 2 with myasthenia gravis (1.3%), one with Raynaud phenomenon (0.7%), one with polymyositis (0.7%), and one with celiac disease (0.7%) [1]. A recent multinational study highlighted the association with acetylcholine receptor antibody positive myasthenia gravis (AChR-MG) [2]. Sixteen patients had both disorders, and four out of five patients whom stored sera where available had AQP4-IgG present 4 to 16 years before NMOSD onset [2]. An...