The -308.1 polymorphism in the promoter region of the tumor necrosis factor gene is associated with ankylosing spondylitis independent of HLA-B27.

OBJECTIVE: To investigate the allele frequencies of 6 polymorphic sites spanning the region of the genome close to the tumor necrosis factor (TNF) gene in a group of HLA-B27 positive patients with ankylosing spondylitis (AS) in the West of Scotland.

METHODS: One hundred sixty-seven patients with AS, 93 healthy controls, and 88 HLA-B27 positive healthy controls, all from the West of Scotland, were typed by polymerase chain reaction (PCR) for 3 restriction fragment length polymorphisms (RFLP) and 3 microsatellite polymorphic sites spanning the TNF gene cluster. The distribution of these alleles was correlated with the presence of extraspinal manifestations such as peripheral joint disease and uveitis.

RESULTS: The frequency of the Nco-1.2 allele was significantly reduced in patients compared to the genetically unselected control population (p < 0.05), but was no different from the HLA-B27 positive controls. However, the -308.1 allele was significantly increased in the patients compared to the HLA-B27 positive controls (p < 0.03).

CONCLUSION: This study confirms the importance of correct matching in genetic analysis in disease association studies, and provides further evidence supporting the involvement of genes other than the MHC class I locus in the pathogenesis and features of AS.