ABSTRACT
Reactive arthritis (ReA) and ankylosing spondylitis (AS) are part o f the so called spondyloarthropathies which also include arthritis/spondylitis with inflammatory bowel disease (IBD) and arthritis/spondylitis with psoriasis. The main link between each other is the association with HLA-B27, the same pattern of peripheral joint involvement with an asymmetrical arthritis predominandy of the lower limbs, and the possible occurence of sacroiliitis, spondylitis, enthesitis and uveitis. ReA and AS attracted special interest in the past because in ReA the triggering bacteria is known and AS is the most frequent disease and the disease with the worst outcome among the SpA. Furthermore, especially the HLA-B27-positive patients with ReA, with arthritis/spondylitis associated with psoriasis or with arthritis/spondylitis associated with IBD develop in about 20-50% of cases the full blown picture of AS in the course of their disease.
