Ankylosing spondylitis

Ankylosing spondylitis (AS) is a long-term inflammatory arthritis that mainly affects the spine and the joints where the spine meets the pelvis. It belongs to a group of conditions called axial spondyloarthritis. In some people the spinal bones slowly fuse together, which limits movement and can cause a stooped posture.

It usually starts in teenagers and young adults. There is no cure, but treatment can control symptoms and slow the disease, and most people can lead productive lives.

Symptoms come on slowly over months or years, and may come and go in flares.

• Pain and stiffness in the lower back, buttocks or hips, often worse at night or after resting, and better with movement and exercise
• Pain and swelling in other joints, such as the ribs, shoulders, knees or feet
• Extreme tiredness
• Difficulty taking a deep breath, if the ribs are affected
• Eye pain and vision changes, from inflammation of the eye (uveitis)
• Weight loss, skin rashes such as psoriasis, and tummy pain with loose stools

See a doctor if back pain and stiffness continue for more than a few weeks, especially if they are worse at night or after rest and ease with movement. Also tell a doctor about pain in other joints, trouble breathing deeply, or any eye problem. If AS is suspected, you will usually be referred to a rheumatologist, a doctor who specialises in arthritis.

The cause is not known. Genes and the environment are both thought to play a part. A gene variant called HLA-B27 raises the risk, but many people who carry it never develop AS.

• Age: most people develop symptoms before 45
• Being male: AS is more common and more severe in men, but women can get it too
• A family history of AS, or carrying the HLA-B27 gene
• Having Crohn's disease, ulcerative colitis or psoriasis
• Smoking, which makes the disease more severe

The outlook varies from person to person. Possible problems include:

• Fusion of spinal bones, causing a stiff, stooped back
• Breathing difficulty, if the rib joints are affected
• Inflammation of the eye (uveitis)
• Thinner bones (osteoporosis) and spinal fractures
• Damage to the hips or knees, sometimes needing joint replacement
• A higher risk of heart and blood vessel disease

AS cannot be prevented, but these steps help protect the spine and make treatment work better:

• Stay active with regular exercise, after checking with a doctor or physiotherapist
• Keep good posture, and ask a physiotherapist about exercises and sleeping positions
• Do not smoke, and ask for help to quit
• Keep to a healthy weight
• Take medicines as prescribed, and keep follow-up visits

No single test confirms AS. A doctor asks about the pain, what makes it better or worse, and whether relatives have back pain or arthritis. They examine the spine, hips, heels and chest, and check how well you bend and breathe deeply.

Tests may include an X-ray, which can take years to show changes, and an MRI, which can show the disease earlier. A blood test for HLA-B27 adds information but does not confirm AS on its own, since many carriers never develop it.

There is no cure, but treatment can relieve symptoms, keep posture, flexibility and strength, and slow the disease. It usually combines exercise, physiotherapy and medicines.

Medicines may include anti-inflammatory pain relief, biological medicines (including anti-TNF medicines) that block the signals causing inflammation, tablets called JAK inhibitors when other treatment has not worked, and steroid injections into a joint. A rheumatologist chooses what suits you. Anti-inflammatory tablets do not suit everyone, so check with a doctor before taking them regularly.

Surgery is uncommon. It may replace badly damaged joints or, rarely, straighten a severely curved spine.