[Anti-MOG + neuromyelitis optica spectrum disorders treated with plasmapheresis]

A 10-year-old boy developed bilateral optic neuritis and myelitis after a suspected viral infection and appendicitis. Magnetic resonance imaging (MRI) showed multiple lesions in both optic nerves, the optic chiasm, and the spinal cord. Several small lesions were also observed in the cerebellum and cerebral white matter. The serum tested negative for anti-aquaporin (AQP)-4 antibody and positive for anti-myelin oligodendrocyte glycoprotein (MOG) antibody. The diagnosis was neuromyelitis optica spectrum disorder (NMOSD). Two courses of high-dose methylprednisolone were administered; however, only a small improvement in his visual acuity was achieved. He underwent 3 courses of plasma exchange to achieve sufficient visual acuity. After the serum anti-MOG antibody titer decreased to the cut-off level, oral prednisolone and azathioprine administration were also stopped, 10 months after onset. Recently, NMO and NMOSD cases positive for anti-MOG antibodies have been reported, which showed clinical features different from those of NMO cases positive for anti-AQP4 antibody. Although most of the reported cases responded to steroid therapy, plasma exchange was required in our case. Further analysis on larger numbers of cases is needed to establish treatments for anti-MOG antibody-positive NMO and NMOSD.