Ankylosing spondylitis: a family study.

Of the first degree relatives of B27 positive spondylitis probands, 10.2% demonstrated an associated disease, i.e., ankylosing spondylitis, Reiter's syndrome, peripheral arthritis, or acute anterior uveitis; all were B27 positive. Eighteen, i.e., only 13.7% of the B27 positive subjects had sacroiliitis; 4 were asymptomatic. We would therefore caution against the previous over-estimation of disease prevalence in "randomly selected" HLA-B27 positive individuals. None of the B27 negative relatives had any uveitis or spondyloarthropathy.