“…Numerous studies have demonstrated that there is an association between ankylosing spondylitis and ulcerative colitis (Steinberg and Storey, 1957;Wilkinson and Bywaters, 1958;Fernandez-Herlihy, 1959;Zvaifler and Martel, 1960;Acheson, 1960;McBride, King, Baikie, Crean, and Sircus, 1963;Wright and Watkinson, 1965;Jayson, Salmon, and Harrison, 1970). The prevalence of these diseases in combination appears to be at least ten and perhaps fifty times greater than would be expected if the association was by chance, on the basis of estimates of prevalence in normal populations (Kellgren, 1964;Evans and Acheson, 1965;Ansell and Lawrence, 1966).…”