The discrepant and in some cases opposite genetic associations described here for some of the DRB1 alleles with non-LS and LS patients are in line with the concept that LS is a distinct disease entity, further supported by the finding of a variant of CCR2 that was recently described to associate with LS patients independently of DRB1*03 [15] There were however also several similarities between non-LS and LS patients, especially regarding the influence of DRB1 alleles on the disease course. This evidence concerns the gene HLA-DRB1 and Leigh syndrome.