Only five alleles, all from the HLA class II region, were significant after the Bonferroni correction; the expressed protective alleles HLA-DRA*01:01:01 and -DQA1*03:01:01 within PD, the risk allele HLA-DQA1*03:03:01 within the Prodrome cohort and the HLA-DRA*01:01:02 and -DRB4*01:03:02 risk alleles in the SWEDD group. The gene discussed is HLA-DRA; the disease is Parkinson disease.