In this report we describe a case of a 19-year-old man with a two-year history of polyarthritis affecting the lower limbs and dactylitis of the toes. His clinical picture fulfilled the new European diagnostic criteria for spondyloarthropathies. Systemic examination revealed a big mass in the left iliac fossa that was found to be due to an acquired functional megacolon. Complete remission of the joint involvement was obtained by treating the bowel disease.