MOG and myeloid sarcoma: Although the occurrence of antibodies directed against myelin oligodendrocyte glycoprotein (MOG) and aquaporin-4 (AQP4) is now considered to be own entities (reviewed by Fujihara et al. [13]), the existence of dysregulated humoral immune activity in MS has been known ever since abnormal production of intrathecally synthesized immunoglobulin (Ig) G in forms of oligoclonal bands (OCBs) was described in the 1940s [14].