Devic's disease or neuromyelitis optica (NMO) is an autoimmune, inflammatory and demyelinating pathology of the central nervous system that affects the optic nerve and the spinal cord. Diagnosis confirmed by imaging, magnetic resonance (MR) and the presence of the anti-aquaporin 4 antibody (anti-AQP4). We describe two cases of patients with mixed connective tissue disease (MCTD) and Devic's disease, who had anti-AQP4 positive and areas with neuroaxis MR abnormalities, showing this rare association.