Studies of myelitis associated with rheumatologic conditions largely predate the availability of MOG-IgG cell-based assays (CBAs)21,22 and widespread use of CBAs for detection of AQP4-IgG, which feature superior sensitivity and specificity compared with ELISA.23,24 Together with the establishment of NMOSD and MOGAD diagnostic criteria,22,25 along with canonical clinical and neuroimaging characteristics that can separate NMOSD and MOGAD from other mimics,26, –, 30 clinicians practicing in the past 5–10 years have more precise tools for diagnosis than in previous decades. This evidence concerns the gene AQP4 and myelitis.