Pidala et al., analyzing a survey of 8003 patients, observed that a single mismatch at HLA-B had a greater risk of grade III-IV acute GvHD, chronic GvHD and a lower risk of relapse compared to single mismatch at HLA-C, with no further statistically significant difference due to the presence of other mismatched loci [19]. This evidence concerns the gene HLA-C and acute graft versus host disease.