We report the case of a 45-year-old Caucasian woman suffering from ankylosing spondylitis and undifferentiated connective tissue disease in whom the prevailing clinical features were retinal vasculitis and inflammatory low back pain. HLA typing revealed the concomitant presence of B27 and DR2 antigens. We hypothesise that the uncommon coexistence of ankylosing spondylitis and connective tissue disease in the same patient could be due to the exceptional association of HLA- B27 with the DR2 antigen.