Spondyloarthritis is any arthritis of the vertebral column. Ankylosing spondylitis (AS) is a specific inflammatory spondyloarthritis with variable involvement of peripheral joints and other organs, especially the eyes. AS is a chronic autoimmune arthritis. It can cause eventual fusion of the spine. Patients with typical features of spondyloarthritis who do not fulfill the criteria for AS are classified as having undifferentiated spondyloarthritis (uSpA).