A group of inflammatory rheumatic diseases associated with arthritis and enthesitis, and often involving the axial skeleton. The most common form of spondyloarthritis is ankylosing spondylitis. Other forms include axial spondyloarthritis, peripheral spondyloarthritis, reactive arthritis, psoriatic arthritis/spondylitis and enteropathic arthritis/spondylitis.

Heterogeneous group of arthritic diseases sharing clinical and radiologic features. They are associated with the HLA-B27 ANTIGEN and some with a triggering infection. Most involve the axial joints in the SPINE, particularly the SACROILIAC JOINT, but can also involve asymmetric peripheral joints. Subsets include ANKYLOSING SPONDYLITIS; REACTIVE ARTHRITIS; PSORIATIC ARTHRITIS; and others.