HLA-DRB1*15 phenotype frequency was higher in DD positive Caucasoids (37.3%) when compared with control data (20.9%) (corrected P=0.029): we conclude that in Caucasoids of European origin, HLA-DRB1*15 is associated with risk of developing DD.
Then, among the genomic variations observed in DD, alterations in the copy number of genes in chromosomal regions 10q22, 16p12.1 and 17p12, associations with the HLA-DRB1*15 allele and a mutation in the rRNA 16s identified in forms with a matrilinear heredity, were reported.