Relapsing neuromyelitis optica in an adolescent girl.

Early differentiation of neuromyelitis optica spectrum disorder (NMO-SD) from multiple sclerosis (MS) is of paramount importance as NMO-SD (especially relapsing variant) has more severe morbidity than MS. We describe a case of an adolescent girl who presented with repeated episodes of optic neuritis over a period of 4 years with normal brain MRI scans. She was treated initially as relapsing remitting MS, before showing clinical evidence of transverse myelitis (TM), and eventually being diagnosed as NMO-SD. Pulse intravenous methyl prednisolone along with immunosuppressive therapy led to remission of her disease. However, delay in diagnosis as NMO-SD led to visual disability in the left eye. Therefore, in young patients with recurrent optic neuritis and normal brain MRI, it may be prudent to get spinal MRI done to look for TM, even when asymptomatic. In addition, we should keep a low threshold for requesting aquaporin-4 antibody testing in these patients.