Unilateral Visual Loss in a Previously Healthy 15-Year-Old Girl: Monosymptomatic Neuromyelitis Optica?

We report a previously healthy 15 year old girl with acute onset of unilateral visual loss consistent with a diagnosis of monosymptomatic optic neuritis. Her symptoms responded well to the use of high-dose intravenous methylprednisolone. With very brief follow-up (2 months) she has had no subsequent difficulties. However, testing was positive for the presence of anti-aquaporin-4 antibodies in both serum and cerebrospinal fluid, which have been associated with neuromyelitis optica (NMO). While NMO antibodies lack complete sensitivity, there is high degree of specificity. Our patient does not meet currently accepted diagnostic criteria for NMO, but is likely at high-risk to develop myelitis or recurrent optic neuritis. There are no evidence-based guidelines for whether this patient should undergo disease-modifying treatment. Based upon the high-risk for clinical relapse, we have recommended immunosuppressive therapy with rituximab (anti-B cell monoclonal antibodies). While randomized trials for patients with this clinical scenario are unlikely, observational studies of a cohort of such patients would provide better guidance on the natural history and merits of disease-modifying therapy.