[Elderly onset case of neuromyelitis optica that developed at the age of 90].

We report a case of neuromyelitis optica (NMO) that was diagnosed at the age of 90. After initially developing visual loss in the right eye, a patient was diagnosed with optic neuritis. Although treatment with methylprednisolone therapy provided relief, 3 months later she developed optic neuritis on the other side. Visual activity recovered after further administration of methylprednisolone. At the age of 91, she presented with muscle weakness of her left extremities. A cervical MRI revealed myelitis with a longitudinally extensive spinal cord lesion from the second to fifth cervical vertebrae. Anti-AQP-4 antibody was detected in her serum. She was diagnosed with NMO and treated with methylprednisolone therapy. Subsequently, she repeatedly relapsed within a short period, developing myelitis once and optic neuritis three times within a year. However, during each hospitalization period, methylprednisolone therapy proved to be effective for relieving her symptoms. As NMO patients with onsets over 60 years of the age have been reported, medical practitioners should be aware that disease onset can occur at extremely older ages, such as 90 years old.