Fingolimod-induced leukoencephalopathy in a patient with neuromyelitis optica spectrum disorder.

Fingolimod (FTY720) is used for reducing the annualized relapse rate and slowing progression of neurological disability in relapsing-remitting forms of multiple sclerosis (MS). However, its safety is not confirmed in patients with neuromyelitis optica spectrum disorder (NMOSD), who characteristically have positive aquaporin-4 (AQP-4) antibody. A 54-year-old female with a relapsing-remitting course of optic neuritis and myelitis for six years, diagnosed initially as MS, had been treated with interferon beta-1b and oral corticosteroid. Magnetic resonance imaging (MRI) consistently revealed lesions on the optic nerve and spinal cord, but never on the brainstem or cerebral white matter during acute exacerbation. After treatment was switched to fingolimod from interferon beta-1b, multiple new lesions appeared at the brainstem and cerebral white matter. Following discontinuation of fingolimod, these lesions completely cleared, concomitantly with clinical improvement. During fingolimod treatment, she was recognized to be positive for AQP-4 antibody. Fingolimod may be contraindicated in patients with NMOSD.