Psoriatic arthritis (PsA), a chronic immune-mediated heterogeneous inflammatory disease characterized by musculoskeletal inflammation (arthritis, enthesitis, spondylitis and dactylitis), usually occurs in patients with psoriasis. The spondyloarthritides (SPs) (of which psoriasis is one) are a group of inflammatory diseases that share an association with the HLA-B27 MHC class I molecule.

Given this association, these diseases are classically regarded as disorders of adaptive immunity.

In bone marrow donation, HLA-B exon 1 dimorphism (HLAB leader) is associated with risk of graft- versus-host disease, relapse and overall survival after unrelated hematopoietic cell transplantation (UHCT), haploidentical UHCT and cord transplantation. In the literature, there are no studies suggesting the involvement of the HLA B leader gene in MS and RPs. The main aim of this study is to compare the presence of the HLA B leader gene between a group of patients with psoriatic arthritis and a healthy group without inflammatory disease.