Overview of the clinical manifestations and classification of spondyloarthritis - UpToDate

INTRODUCTION The term spondyloarthritis (SpA) is used for a family of disorders, including ankylosing spondylitis (AS, radiographic axial spondyloarthritis [r-axSpA]), nonradiographic axial spondyloarthritis (nr-axSpA), forms of arthritis associated with psoriasis and with inflammatory bowel diseases, and other conditions. The different forms of SpA share a group of clinical features; the most distinguishing features are inflammation of axial joints (especially the sacroiliac [SI] joints), asymmetric oligoarthritis (especially of the lower extremities), dactylitis (sausage digits), and enthesitis (inflammation at sites of ligamentous or tendon attachment to bone). Compared with the general population, patients with SpA have higher frequencies of the human leukocyte antigen (HLA) B27, and of sacroiliitis by radiography or magnetic resonance imaging (MRI) [1]. (See 'Major musculoskeletal features' below and 'Laboratory findings' below and 'Imaging' below.) Additional features include ski

INTRODUCTION The term spondyloarthritis (SpA) is used for a family of disorders, including ankylosing spondylitis (AS, radiographic axial spondyloarthritis [r-axSpA]), nonradiographic axial spondyloarthritis (nr-axSpA), forms of arthritis associated with psoriasis and with inflammatory bowel diseases, and other conditions. The different forms of SpA share a group of clinical features; the most distinguishing features are inflammation of axial joints (especially the sacroiliac [SI] joints), asymmetric oligoarthritis (especially of the lower extremities), dactylitis (sausage digits), and enthesi