Non-HLA-B27 genetic factors in HLA-B27 associated diseases.

Family and twin studies showed that besides HLA-B27 other genetic factors are of significance for the pathogenesis of ankylosing spondylitis, reactive arthritis or acute anterior uveitis. There are up to now no strong indications that any subtype of B27 is especially associated with these diseases. Also the indications that B2703 and B2706 are protective should be further substantiated. HLA-B27/HLA-B60 heterozygotes have a three times higher risk to develop ankylosing spondylitis as persons with another B type opposite B27. Haplotype studies made it unlikely that the other genetic factors are situated on chromosome 6p. Studies on 23 other genetic marker systems were all negative in this respect.