A comparative study of HLA genes in HLA–B27 positive ankylosing spondylitis and HLA–B27 positive peripheral reactive arthritis

OBJECTIVE: To determine whether HLA-B27 positive patients with ankylosing spondylitis (AS) and reactive arthritis (ReA) share additional HLA factors that confer disease susceptibility. METHODS: HLA class I antigens were typed serologically, and class II antigens molecularly, in samples taken from 33 patients with AS, 30 patients with ReA, and 55 healthy HLA-B27 positive controls. RESULTS: There was no major difference between the HLA alleles in AS and ReA patients, but deviations were observed when compared with healthy controls, especially between the antigens that were probably encoded by genes in the non-B27 chromosome. CONCLUSION: These results suggest that both HLA class I and class II genes may influence the pathogenesis of HLA-B27 positive ReA, whereas class I antigens seem to be the major additional genetic factors in HLA-B27 positive AS.