Furthermore, APS has been described in overlap with neuromyelitis optica spectrum disorder (NMOSD) (94, 95), another autoimmune condition characterized by recurrent episodes of optic neuritis and longitudinally extensive transverse myelitis (that is, extended over 3 or more spinal cord segments) and positivity for anti-aquaporin-4 (anti-AQP4) or anti-myelin oligodendrocyte glycoprotein (anti-MOG) (96). This evidence concerns the gene AQP4 and neuromyelitis optica.