In 2007, the term NMO spectrum disorders (NMOSD) was introduced to include AQP4‐Ab seropositive patients with limited or inaugural forms of NMO: first‐attack LETM, recurrent or bilateral ON (Wingerchuk, Lennon, Lucchinetti, Pittock, & Weinshenker, 2007). Here, AQP4 is linked to neuromyelitis optica.