Ankylosing spondylitis
A chronic inflammatory arthritis that mainly affects the spine and the joints where the pelvis meets the spine. It causes gradual-onset back pain and stiffness that is worse with rest and better with movement, typically starting in young adulthood, and can, over years, fuse parts of the spine.
What it is
Ankylosing spondylitis is a form of axial spondyloarthritis — a chronic autoimmune inflammatory disease that primarily targets the spine and the sacroiliac joints (where the base of the spine meets the pelvis). Unlike ordinary mechanical back pain, its pain is inflammatory: it begins gradually, usually before the age of 45, is worse in the second half of the night and on waking with prolonged morning stiffness, improves with exercise rather than rest, and responds well to anti-inflammatory medication. It is strongly linked to a genetic marker called HLA-B27, though carrying that gene does not mean the disease will develop. Over years, ongoing inflammation can lead to new bone formation that gradually stiffens and, in some people, fuses segments of the spine, reducing flexibility and posture. Beyond the spine it can involve the hips and shoulders, cause inflammation where tendons attach to bone (enthesitis, such as heel pain), and is associated with painful red eyes (uveitis), psoriasis and inflammatory bowel disease. Blood tests may show raised inflammatory markers (ESR, CRP), but these can be normal, so diagnosis relies heavily on the pattern of symptoms and on imaging (MRI or X-ray) of the sacroiliac joints. Modern treatment — exercise, anti-inflammatories and, when needed, biologic medicines — controls symptoms well and helps preserve mobility.
Key lab markers
- ESR and CRP — inflammatory markers; may be raised, but are often normal and do not exclude the disease.
- hs-CRP — a more sensitive inflammation measure sometimes used to track activity.
- HLA-B27 genetic marker — strongly associated and supports the diagnosis, but not measured in this catalog and not required to have the disease.
- Imaging (MRI / X-ray of sacroiliac joints) — central to diagnosis; blood tests alone cannot confirm it.
- Full blood count — may show anemia of chronic inflammation.
Symptoms
- Gradual-onset lower back and buttock pain, often alternating sides
- Marked morning stiffness that eases with movement
- Back pain that is worse with rest and better with exercise
- Night pain, especially in the second half of the night
- Reduced spinal flexibility over time
- Heel or other tendon-insertion pain (enthesitis)
- Painful, red eye (uveitis) in some people
- Fatigue
Related symptoms
Related lab panels
When to discuss with a doctor
See a doctor about back pain that starts gradually before age 45, lasts more than three months, comes with significant morning stiffness, wakes you in the night and improves with movement rather than rest — this inflammatory pattern is different from ordinary mechanical back pain and warrants assessment for spondyloarthritis, ideally by a rheumatologist. A painful red eye, or a personal or family history of psoriasis or inflammatory bowel disease, adds to the picture. Early diagnosis matters because exercise and modern treatments control symptoms and help preserve movement and posture. Mediora.AI can highlight raised inflammatory markers that fit the picture, but these are often normal in ankylosing spondylitis, so a normal result does not rule it out — the diagnosis rests on the symptom pattern and imaging, assessed by your doctor.