AQP4 and Miosis: On the other hand, disturbances in pupillary function, including miosis, have been repeatedly reported also in AQP4-IgG-positive NMO [245–249], and the periaqueductal area, believed by some authors to contain the mostly likely site of damage in patients with Argyll Robertson syndrome, is also a site of high AQP4 expression and, accordingly, not infrequently a site of inflammation in AQP4-IgG-positive NMO [9, 250].