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Abstract
Neuromyelitis optica is an inflammatory demyelinating disease with generally poor
prognosis that selectively targets optic nerves and spinal cord. It is commonly misdiagnosed
as multiple sclerosis. Neither disease has a distinguishing biomarker, but optimum
treatments differ. The relation of neuromyelitis optica to optic-spinal multiple sclerosis
in Asia is uncertain. We assessed the capacity of a putative marker for neuromyelitis
optica (NMO-IgG) to distinguish neuromyelitis optica and related disorders from multiple
sclerosis.
Indirect immunofluorescence with a composite substrate of mouse tissues identified
a distinctive NMO-IgG staining pattern, which we characterised further by dual immunostaining.
We tested masked serum samples from 102 North American patients with neuromyelitis
optica or with syndromes that suggest high risk of the disorder, and 12 Japanese patients
with optic-spinal multiple sclerosis. Control patients had multiple sclerosis, other
myelopathies, optic neuropathies, and miscellaneous disorders. We also established
clinical diagnoses for 14 patients incidentally shown to have NMO-IgG among 85000
tested for suspected paraneoplastic autoimmunity.
NMO-IgG outlines CNS microvessels, pia, subpia, and Virchow-Robin space. It partly
colocalises with laminin. Sensitivity and specificity were 73% (95% CI 60-86) and
91% (79-100) for neuromyelitis optica and 58% (30-86) and 100% (66-100) for optic-spinal
multiple sclerosis. NMO-IgG was detected in half of patients with high-risk syndromes.
Of 14 seropositive cases identified incidentally, 12 had neuromyelitis optica or a
high-risk syndrome for the disease.
NMO-IgG is a specific marker autoantibody of neuromyelitis optica and binds at or
near the blood-brain barrier. It distinguishes neuromyelitis optica from multiple
sclerosis. Asian optic-spinal multiple sclerosis seems to be the same as neuromyelitis
optica.