Juvenile ankylosing spondylitis and HLA B27 homozygosity.

Ten consecutive patients with juvenile ankylosing spondylitis were investigated in a prospective study. At least one of the parents of each patient had a positive history of probable or definite ankylosing spondylitis, Reiter's syndrome, or acute anterior uveitis. The patients and their parents were examined clinically and were HLA-typed. Nine of the 10 patients exhibited the genetic marker HLA B27, but only one patient was homozygous for HLA B27. This prevalence of homozygosity among HLA B27 positive persons could be expected to occur by chance alone. Based on the limited material studied, we cautiously conclude that HLA B27 homozygosity is probably not responsible for disease onset in childhood.