RGMA and myeloid sarcoma: Repulsive guidance molecule-a (RGMa) is a membrane-associated glycosylphosphatidylinositol-anchored glycoprotein that has been implicated in various central nervous system (CNS) disorders, including MS (12–14), spinal cord injury (15, 16), stroke (17), and neuromyelitis optica (18–20), both in experimental animal models (12–19) and in patients (12, 13, 16, 19, 20).