HLA-B51 refers to a specific human leukocyte antigen allele present in the HLA-B locus. The significance of this genomic region is that it codes for proteins involved in the immune system. The HLA-B51 association shows a higher prevalence with some autoimmune diseases, mainly Behçet’s disease, presenting with recurrent genital ulcers, skin lesions, and uveitis. HLA typing for HLA-B51 helps evaluate genetic predisposition.