Although the NMO phenotype can occur in contexts of MS or several systemic autoimmune diseases, it is considered a distinct syndrome, especially since the identification of the disease-specific antibody anti-aquaporin 4 (AQP4-Ab, or NMO-Ig) in more than 70% of patients with Devic’s disease[4]. The gene discussed is AQP4; the disease is myeloid sarcoma.