Autoimmune Conditions: Ankylosing Spondylitis.

Ankylosing spondylitis (AS) is a rare yet significant cause of back pain in young adults that often is overlooked. AS should be suspected if symptoms of inflammatory back pain are present or if the patient has a personal or family history of related conditions. X-rays are the initial imaging modality of choice. If suspicion of AS remains high but no sacroiliitis is present on x-ray, an HLA-B27 test should be obtained. The Assessment of SpondyloArthritis International Society (ASAS) criteria are helpful in the diagnosis of AS. Continuous use of nonsteroidal anti-inflammatory drugs is the first-line therapy, followed by tumor necrosis factor-alpha inhibitors, followed by slow-acting antirheumatic drugs (eg, methotrexate). Patients also should undergo physical therapy and, if applicable, should quit smoking and maintain a healthy weight. Patients with AS are at increased risk of complications, such as spinal fracture. Other conditions associated with AS include anterior uveitis, inflammatory bowel disease, and osteoporosis.