In Sardinia, two distinct extended haplotypes harbouring HLA-B*51:01 were identified: A2-Cw2-B*5101-DRB1*11-DQA1*05-DQB1*03, which marks the B*51 positive patients with BD in Sardinia, and A2-Cw2-B*5101-DRB1*04-DQA1*03-DQB1*03, which is significantly more frequent in Sardinian HC than in BD [13]. Here, HLA-B is linked to Behcet disease.