HLA-B and psoriatic arthritis: Allele HLA B27 has been associated with several types of arthritis disorders such as ankylosing spondylitis, reactive arthritis and psoriatic arthritis.48 Other studies have shown that similarity in certain regions of the HLA-B gene between the mother and the daughter give an increased risk of schizophrenia to the daughter.49 Aside from genetic associations, HLA-B may play a role in the two diseases by its involvement in the natural killer cell pathway.