[Polyarthritis flare in patient with ankylosing spondylitis treated with infliximab].

Over the last ten years, the treatment of seronegative spondyloarthropathies has changed dramatically with the introduction of the anti-tumor necrosis factor alpha (TNFα) agents. Nevertheless, there is a growing number of studies describing several adverse reactions in patients treated with biological agents. In the present report we describe the case of a 22-year-old male patient with ankylosing spondylitis who developed a "paradoxic" adverse reaction, while receiving infliximab.