Neuromyelitis optica IgG serostatus in fulminant central nervous system inflammatory demyelinating disease

Background: The aquaporin-4-specific serum autoantibody neuromyelitis optica (NMO) IgG is a validated biomarker distinguishing NMO spectrum disorders from multiple sclerosis (MS). Because fulminant attacks are more common in NMO spectrum disorders than in MS, some investigators suggest thatNMOIgG may be a marker of destructive demyelination rather than a diseasespecific biomarker. To our knowledge, this study is the first to compareNMOIgG serostatus among patients with fulminant central nervous system inflammatory demyelinating disease (CNS IDD). Objective: To determine whether NMO IgG distinguishes patients withNMOspectrum disorders from those with other fulminant corticosteroid-refractory CNS IDD. Design: Descriptive historical cohort. Setting: Neuroimmunology laboratory and neurology practice, Mayo Clinic College of Medicine, Rochester, Minnesota. Patients: Serum samples from 74 patients who underwent plasmapheresis between February 24, 1993, and November 22, 2007, for a corticosteroid-refractory CNS IDD were tested for NMO IgG by indirect immunofluorescence assay. Main Outcome Measures: Two blinded observers scored serum samples tested at 1:120 dilution. Clinical data were obtained by medical record review. Results: Preplasmapheresis serum samples were available from 74 patients (ratio ofwomento men, 2:5); themean interval between blood draw and plasmapheresis was 13 days. At the time of plasmapheresis, the mean age of patients was 46 years (age range, 7-80 years); the mean Expanded Disability Status Scale score was 7.0 (score range, 3.5-9.5 [10.0 is death]). Diagnoses included MS (18 patients with definite and 11 patients with probable), longitudinally extensive transverse myelitis involving at least 3 vertebral segments (20 patients),NMO(14 patients), transverse myelitis involving fewer than 3 vertebral segments (8 patients), optic neuritis (2 patients), and acute disseminated encephalomyelitis (1 patient). Neuromyelitis optica IgG was detected in 20 patients (27%) (10 with longitudinally extensive transverse myelitis, 9 withNMO,and 1 with recurrent optic neuritis) and was not detected in any patient with MS, short transverse myelitis, monophasic optic neuritis, or acute disseminated encephalomyelitis. Conclusion: Neuromyelitis optica IgG is a specific biomarker for NMO spectrum disorders and is not simply a marker of destructive CNS IDD.