HLA-DRB1 and myeloid sarcoma: Intriguingly, the genotyping of HLA-DRB1, comparing the patients based on disease onset (before or during the COVID-19 pandemic and related or unrelated to SARS-CoV-2 vaccination), revealed that none of the MS patients with demyelinating event onset within one month after COVID-19 vaccination expressed the HLA-DRB1*15 allele.