Observations of absent or very low levels of conformational MOG-Ab in MS patients, and reports of imaging features distinct from MS, supports that MOG-Ab disease is a separate clinical entity from both MS and AQP4-Ab NMOSD, although pathological biomarkers have not been explored up to now [21, 22, 42, 52]. The gene discussed is AQP4; the disease is myeloid sarcoma.