Spondyloarthritis is an inflammatory arthritis that affects the axial, or central, skeleton. The back pain of spondyloarthritis tends to worsen with activity and improve with rest. It shares a genetic overlap with skin psoriasis, inflammatory bowel disease, and inflammatory eye disease. As a result, individuals with spondyloarthritis are more likely to have these conditions, as well as arthritis of smaller joints and irritations of tendons and connective tissue (such as plantar fasciitis).
The disease typically begins before the age of 40 and has a hereditary component, meaning that spondyloarthritis can afflict multiple family members. The diagnosis is made by considering a persons medical history, the pattern of their symptoms, x-rays and/or magnetic resonance imaging. Blood markers of inflammation and a genetic test called HLA-B27 may help clarify the diagnosis, though these tests are imprecise and as a result do not confirm the diagnosis.