Ankylosing spondylitis (AS) is a chronic inflammatory spinal disease characterized by joint pain and progressive stiffness in the cervical (neck), thoracic (mid-back), lumbar (low back), and sacroiliac joints (sacrum).
AS is categorized by enthesopathy, which means an inflammatory attack where tendons and ligaments attach to bones or joint capsules (called enthesis). In the spine, the primary site for this enthesis is where the long spinal ligament (anterior longitudinal ligament) attaches to the front of the vertebrae. Inflammation of the enthesis is called enthesitis.
The onset of AS is usually seen in people ages 15 to 45 years. Early symptoms may be similar to arthritis; low back and buttock pain and stiffness that are worse in the morning and night. Some patients experience loss of appetite and mild fevers.
Progression of Ankylosing Spondylitis
Over months or years, pain may spread up the spine and into the neck. As the disease progresses, the body's defense mechanisms fight back by producing new bone (ossification). The new bone grows between and around the vertebrae, causing abnormal fusion and increases the risk for spinal fracture.
Sometimes ankylosing spondylitis leads to a spinal deformity such as a humpback (abnormal kyphosis) or swayback (abnormal lordosis). Advanced symptoms can be chronic and include severe pain and stiffness of the spine and possibly other body joints. Bowel (Chrohn's disease) and eye inflammation (iritis, uveitis) may be associated with ankylosing spondylitis.
Treatment may include: