Purpose: It has recently been reported that the anti-aquaporin-4 antibody (AQP4-Ab) can be a specific marker of neuromyelitis optica. We present three cases of optic neuritis (ON) where the patients tested positive for AQP4-Ab, but showed no neurological signs.
Methods: Sera were obtained from 32 Japanese patients with ON and no other neurological abnormalities (mean age 46 +/- 20 years). AQP4-Ab was detected by indirect immunofluorescence staining using human-AQP4-transfected HEK 293 cells.
Results: AQP4-Ab was positive in three female patients (aged 9, 64 and 82 years). Their illness was characterized by bilateral severe optic nerve involvement, insufficient visual recovery, and autoimmune abnormalities (such as positive antinuclear antibody). Two of these patients experienced recurrent episodes of ON. In at least two episodes, the intracranial portion of the optic nerve showed significant inflammation on magnetic resonance imaging.
Conclusions: These cases indicate that some ON patients have an immunological pathogenesis similar to that seen in neuromyelitis optica. In addition, examination for AQP4-Ab positivity in the initial phase of ON is important in predicting the prognosis, including the possibility of the development of transverse myelitis.