AQP4, the main target antigen in NMO, is expressed both in the nasal olfactory mucosa including the basal cells, the supporting cells, and the Bowman glands that are part of the olfactory epithelium as a microenvironment necessary for olfaction [12] and in the astrocytic endfeet sealing the microvasculature, and the pial surface of the olfactory bulb; accordingly, we found a strong staining of the olfactory bulb by AQP4-IgG-positive NMO sera (see Figures 1 and 2). Here, AQP4 is linked to neuromyelitis optica.