The involvement of the OC in ON lesions has been well documented in cases of AQP4 + NMOSD, but it is less common in MS and MOGAD.2,15 Despite these differences, in our population we observed that ON+ AQP4 + NMOSD and MOGAD had lower MTR values when compared to HCs. The gene discussed is AQP4; the disease is myeloid sarcoma.