Concurrent rheumatoid arthritis and ankylosing spondylitis in one patient: the importance of new classification criteria.

We report the case of concomitant ankylosing spondylitis and rheumatoid arthritis in a 65-year-old Caucasian male, who had symmetric polyarthritis with erosion of the metacarpophalangeal joint on conventional X-ray, inflammatory low back pain with HLA-B27 positivity, and sacroiliitis. Laboratory analysis showed high levels of rheumatoid factor and anti-cyclic citrullinated peptide antibody (anti-CCP). Clinical features of previously reported cases were compared with those of our case. This is the first case report on the coexistence of both diseases in the same patient, for whom anti- CCP testing and the latest versions of axial ASAS criteria and ACR/EULAR criteria for the classification of ankylosing spondylitis and rheumatoid arthritis, respectively, were used.