Most of the CBA tests reported for NMO-IgG detection are based on the use of the AQP4-M1 coding sequence (CDS) [19], [20], [21], [22], which is also able to produce the AQP4-M23 isoform through a mechanism of leaky scanning (LS) [6], [23]. The gene discussed is AQP4; the disease is neuromyelitis optica.