[Myasthenia gravis complicated with optic neuritis showing anti-aquaporin 4 antibody: a case report].

We report a 33-year-old woman with myasthenia gravis (MG) who developed optic neuritis after the treatment of MG for 22 years. At 10 years of age, she was diagnosed with generalized MG (MGFA V) and at 11 years, she underwent thymectomy. She had been treated successfully only with anti-cholinesterase inhibitors for 22 years despite lasting high titer of anti-acetylcholine receptor antibody. She could manage everything in her life and had two children. At 33 years of age, she experienced acute visual loss in her left eye. Laboratory examination showed positive anti-acetylcholine receptor, antinuclear, anti-ssDNA, anti-dsDNA, anti-SS-A, and anti-aquaporin 4 (AQP4) antibodies. Brain MRI showed an enlarged left optic nerve with enhancement by gadolinium. Three courses of steroid pulse therapy did not show any effect on her visual acuity. However, plasma exchange therapy mildly ameliorated her visual acuity. Her MG symptoms were not exacerbated during the course of the optic neuritis. Furthermore blephalopstosis caused by MG has disappeared completely after the treatment with steroid pulse and plasma exchange. This case had 23 years of immunosuppressive treatment free durations with stable condition. The cause of development of optic neuritis would be her predisposed tendency other than thymectomy or treatment with immunosuppressive therapies.