MOG and myeloid sarcoma: In 2018, international recommendations suggested restricting MOG-IgG testing to patients with clinical and paraclinical findings that were typical of MOGAD and/or atypical for multiple sclerosis (MS).3 At this time, established acute demyelinating syndromes compatible with MOGAD included optic neuritis, myelitis, brainstem demyelination, and acute disseminated encephalomyelitis (ADEM).