Other clinical manifestations include peripheral arthritis, enthesitis, and extra-articular organ involvement.
AS is the prototype of the spondyloarthropathies, a family of related disorders that also includes reactive arthritis (Re A), psoriatic arthritis (Ps A), spondyloarthropathy associated with inflammatory bowel disease (IBD), undifferentiated spondyloarthropathy (USp A), and, possibly, Whipple disease and Behçet disease (see the image below).
This disorder probably represents an earlier phase or milder form of AS.
Undifferentiated spondyloarthropathy (USp A) is used to describe patients with predominantly peripheral features and may represent an early phase or incomplete form of AS or another spondyloarthropathy.
Fatigue is another common complaint, occurring in approximately 65% of patients with AS.
Increased levels of fatigue are associated with increased pain and stiffness and decreased functional capacity.Magnetic resonance imaging (MRI) or computed tomography (CT) scanning of the SI joints, spine, and peripheral joints may reveal evidence of early sacroiliitis, erosions, and enthesitis that are not apparent on standard radiographs.Ankylosing spondylitis (AS) is a chronic, multisystem inflammatory disorder primarily involving the sacroiliac (SI) joints and the axial skeleton.Pulmonary involvement is secondary to inflammation of the costovertebral and costotransverse joints, which limits chest-wall range of motion (ROM).Pulmonary fibrosis is generally an asymptomatic incidental radiographic finding.Thus, they may play an important role cells in the pathogenesis of AS and other spondyloarthropathies.Another possible mechanism in the induction of AS is presentation of an arthritogenic peptide from enteric bacteria by specific HLA molecules.Peripheral joints and entheses and certain extra-articular organs, including the eyes, skin, and cardiovascular system, may be involved to a lesser degree. Cytokines, particularly tumor necrosis factor-α (TNF-α) and transforming growth factor-β (TGF-β), are also important in the inflammatory process by leading to fibrosis and ossification at sites of enthesitis.The initial presentation of AS generally relates to the SI joints; involvement of the SI joints is required to establish the diagnosis.Treatment measures include pharmacologic, physical therapy, and surgical.The spondyloarthropathies are chronic inflammatory diseases that most commonly involve the SI joints and the axial skeleton, with hip and shoulder joints less frequently affected.