HLA-DRB1 and Epstein-Barr virus infection: These diseases share several genetic and environmental factors, in particular the predisposing effect of certain HLA-DRB1 alleles (although not exactly identical alleles), the predisposing effect of EBV infection and of factors, which can be related to EBV infection (e.g. vitD deficiency) (Table 2) (106, 107, 160–171).