In a nationwide French cohort of 197 patients with an incident or retrospective diagnosis of MOG-Ab-positive acquired demyelinating syndromes, only 19.3% met diagnostic criteria for NMOSD and 1.5% for MS at the last follow-up, which precipitated the separation of MOGAD as an entity of its own [13,14]. The gene discussed is MOG; the disease is myeloid sarcoma.