Our aim has been to analyze the relationship between different MS risk factors (HLA-DRB1*15:01 allele, sun exposure, vitamin D level, skin tone, and smoking habit) in independent cohorts from Spain, from three different provinces, with important differences in latitude, and thus, significant differences in UVR and erythemal index (Figure 1). The gene discussed is HLA-DRB1; the disease is myeloid sarcoma.