Recurrent hyperCKemia with normal muscle biopsy in a pediatric patient with neuromyelitis optica

Neuromyelitis optica (NMO) is a demyelinating disease of the CNS that preferentially affects the optic nerve and spinal cord.1 The presence of circulating autoantibodies (NMO–immunoglobulin G [IgG]) having the water channel aquaporin-4 (AQP-4) as their target antigen is associated with NMO.1 Outside the CNS AQP-4 is present in the distal collecting tubes of the kidney, in parietal cells of the stomach,2 and in fast-twitch fibers of skeletal muscle.3 Several findings support the idea that AQP-4 water channels may be associated to the dystrophin-glycoprotein complex (DGC) in skeletal muscle fibers and AQP-4 expression has been found altered in muscle diseases.4