The clinical and radiological characteristics and serostatus of neuromyelitis optica (NMO)-IgG in 87 children with inflammatory demyelinating CNS disorders were analyzed in a study at the Mayo Clinic, Rochester, MN, and other centers in the US, Canada, and Argentina. Seventeen patients had NMO and of these, 8 (47%) were seropositive. The prevalence of seropositivity was higher with relapsing NMO (7 of 9, 78%) than monophasic NMO (1 of 8, 12.5%, p=0.01). The majority of children with NMO (14 of 17) were enrolled from the program in Argentina, and few came from Canada. None showed oligoclonal bands in the CSF. MRI abnormalities were revealed in 9 (53%). After a follow-up of 36 months (range 1.2-126 months), 6.3% children with NMO were wheelchair-bound and 23% had severe visual impairment. One of 5 children with relapsing optic neuritis and none of 8 with monophasic optic neuritis was seropositive. Among 41 with relapsing-remitting multiple sclerosis, 9 with transverse myelitis, and 3 with ADEM, none was seropositive. The frequency of NMO-IgG in children is similar to that in adults. Longitudinally extensive spinal lesions on MRI are not as predictive of NMO in children as in adults. 
COMMENT. Neuromyelitis optica is characterized by monophasic or recurrent episodes of optic neuritis and longitudinally extensive transverse myelitis, either monophasic or recurrent. The autoantibody NMO-IgG is present in 73% of adults with NMO and is 92% specific for NMO and related disorders, recurrent optic neuritis or transverse myelitis. In children with NMO in the above study, 47% were seropositive. The role of NMO-IgG autoantibody in NMO is unknown, but it may be important in recurrent disease. An overview of NMO in children is provided in an editorial. 
The most useful diagnostic feature of NMO or NMO-spectrum disorders in adults is a longitudinally extensive spinal cord lesion. This contrasts with the well-circumscribed foci of increased T2-weighted signal in multiple sclerosis, typically seen in adults. In children with MS, the discrete spinal lesions are common, but 14% also show the longitudinally extensive spinal lesions, rare in adults with MS. A longitudinally extensive spinal lesion in a child with demyelinating disease does not exclude a diagnosis of MS and is less predictive of an NMO-spectrum disorder than in adult patients.
Relationship between NMO and autoimmune disease. The association of NMO-IgG and non-organ-specific autoantibodies in patients with systemic lupus erythematosis (SLE) and in those with NMO spectrum disorder was evaluated at the Mayo Clinic and University of Lille, France . Patients with NMO were seropositive for NMO-IgG, and those with SLE without NMO were seronegative for this autoantibody. NMO-IgG is specific for distinguishing NMO spectrum disorder from multisystem autoimmune disorders. NMO may coexist with SLE and other autoimmune disease and is not a complication of SLE.