AQP4 and myeloid sarcoma: In MS, white matter lesions tend to affect specific brain regions, such as the periventricular and juxtacortical white matter, the corpus callosum and the infratentorial areas; in NMOSD-AQP4, brain lesions are mostly located in areas with high AQP4 expression (e.g., periependymal lesions surrounding the ventricles or involving corticospinal tracts) [8].