With regard to advanced MRI markers, cortical lesions are well described as distinctive features of MS,18 whereas they are rarely seen in AQP4-NMOSD and MOGAD.19,20 The central vein sign (CVS) is detectable in a higher percentage of brain lesions in RRMS than AQP4-NMOSD21 and MOGAD.22 Gray matter atrophy is seen in MS, but not in NMOSD23; it is unknown whether gray matter volumes distinguish between RRMS and MOGAD. Here, AQP4 is linked to myeloid sarcoma.