Introduction: Ankylosing spondylitis is a chronic inflammatory disorder that is rarely associated with severe systemic manifestations.
Exegesis: We report the case of a 29-year-old man presenting with an atypical ankylosing spondylitis. The patient presented with a high spiking fever, a marked weight loss, and an unusual increase of acute phase response markers. Such features are rarely associated with ankylosing spondylitis and the review of the few similar reported cases in the literature showed that this presentation is usually associated with a severe disease course, and an asymmetrical joint involvement that is unresponsive to nonsteroidal anti-inflammatory agents.
Conclusion: Clinicians should be aware of this unusual presentation of ankylosing spondylitis, which should be included in the list of aetiologies of fever of unknown origin, to avoid useless diagnostic procedures. The severity of the disease course may lead to the consideration of a more aggressive treatment strategy.