Genetics of HLA associated disease: ankylosing spondylitis.

We studied families of 30 HLA-B27 positive probands with ankylosing spondylitis (AS) and related spondyloarthropathies (SPA) to investigate any possible discordance between B27 allele and disease presence. Among the 100 relatives studied, B27 was present in all 31 relatives affected with AS or SPA. Our results are in agreement with those of other family studies and do not confirm a recent report of existence of high discordance between B27 allele and AS within multiple case families.