HLA Antigens in Filipinos with Ankylosing Spondylitis

Ankylosing spondylitis has been shown to be highly associated with HLA-B27 in Caucasian patients. This is also present in other ethnic groups. This study was conducted to determine the frequency distribution of HLA antigens in Filipinos and determine the association of ankylosing spondylitis. Twenty patients satisfying the criteria for ankylosing spondylitis and 192 unrelated controls were HLA-A and B typed. Blood from these subjects were typed using NIH lymphocyte microcyto-toxicity method. Of the unrelated controls, the frequencies of HLA A9 (w24), B40, A1, B5, Bw22 were increased and B13, B18, Bw35 were decreased. B27 had a frequency of 5.2%. A very significant high frequency of B27 (90%) was found in patients with ankylosing spondylitis with a very high relative risk of 163. A11 had a frequency of 55% with a relative risk of 3.37 which was not significant while B18 had an 18% frequency and a relative risk of 10.5 which was significant. This study reaffirms the high degree of association of ankylosing spondylitis with HLA B27 and suggests than B18 may be an additional genetic marker for this disease.