This study evaluated the development of MS in groups of individuals who carried HLA-DRB1*15 and lacked HLA-A*02, which are genetic conditions that increase the susceptibility of MS (OR of 4.5). These patients presented a 7.7- fold higher chance of developing MS if exposed to ETS when compared to non-smokers never exposed to ETS without these HLA genotypes. This evidence concerns the gene HLA-A and myeloid sarcoma.