Ankylosing spondylitis


Ankylosing spondylitis, known worldwide outside of German as axial spondyloarthritis, is a chronic inflammatory disease of the entire spine and the sacroiliac joints.

Depending on the form, a distinction is made between two forms: ankylosing spondylitis (severe form) and non-radiographic axial spondyloarthritis (early form and milder form). Together with other forms of arthritis (inflammatory rheumatic joint diseases) which may be associated with the hereditary factor HLA-B27, ankylosing spondylitis belongs to the group of spondyloarthritides. The disease cannot be cured. However, good disease management is possible with the cooperation of the sick person and with targeted drug treatment.

Overview: What is ankylosing spondylitis?

“Ankylosing” means stiffening, “spondylitis” means inflammation of the vertebrae; thus ankylosing spondylitis is the increasing stiffening of parts of the vertebrae due to progressive inflammation. Due to a malfunction of the immune system, the tendon insertions on the spine and pelvis, among other things, are attacked: a focus of inflammation develops.

The disease often begins with an inflammation in the pelvic area, in the joint between the sacrum and ilium (sacroiliitis). Recurrent inflammation can lead to destruction of the joint and fusion/ossification of the joint part (ankylosis). In the area of the spine, ossifications at the sides between the vertebrae can lead to increasing stiffness of the back. Inflammation of joints and tendon attachments in the periphery are also part of the clinical picture.

Other areas of the body can also be affected by the inflammatory developments, for example the iris of the eye or other organs. The disease, which progresses in episodes, can be managed very well on the back with targeted exercise therapy. However, the accompanying severe pain often has to be treated with medication. Fortunately, many patients do not develop ossification at all, so that a distinction is now made between the milder form (non-radiographic axial spondyloarthritis) and ankylosing spondylitis (also known as the radiographic form).

Ankylosing spondylitis – history and incidence

The discovery of bones with significant changes that can be clearly attributed to ankylosing spondylitis proves that this form of arthritis has been with humans for several thousand years. There have been various records of symptom areas since the 17th century. The first detailed description dates back to 1893 by Wladimir Bechterew. Up to two percent of the population are probably affected by spondyloarthritis. In most cases, however, the symptoms are so mild and possibly misinterpreted that only a small proportion of those affected receive a diagnosis and are treated accordingly.

Ankylosing spondylitis: causes and risk factors

There is still no definitive answer as to how ankylosing spondylitis is triggered. What is certain, however, is that a certain hereditary factor significantly increases the risk of developing the disease. This characteristic is called HLA-B27. It is responsible for various processes of the immune system, although the exact mechanism still remains a mystery despite over 50 years of intensive research. HLA-B27 is found in 80 percent of ankylosing spondylitis patients.

However, as around eight percent of the population carry the molecule without ever suffering from any rheumatic disease, researchers assume that other factors also play a role. Among other things, in spondyloarthritis the immune system is directed against its own tissue, for example against tendon insertions. In addition, some studies also suggest that the intestinal flora is involved. Overall, the causes of ankylosing spondylitis are thought to be hereditary, with infections and smoking also playing a role.

Symptoms: Ankylosing spondylitis

In the early stages, ankylosing spondylitis manifests itself through various general back complaints. Beginning in late adolescence or early adulthood, morning stiffness and a dull ache in the lumbar and gluteal region accumulate, with the discomfort decreasing with movement. An intermittent course with respective deteriorations is possible. After the initial diffuse symptoms, various symptoms can be attributed to ankylosing spondylitis:

  • Back pain: Inflammation of the spine and sacroiliac joint leads to immobility – especially in the morning – and considerable pain in the lower back and buttocks, especially after prolonged rest.
  • Pain in the buttocks: This mainly affects the area of the sacroiliac joint. This naturally less mobile connection in the pelvis, which is reinforced by ligaments, causes considerable pain in the buttocks during a rheumatic process. The pain can radiate into the back of the thigh up to about knee height and alternate sides.
  • Pain in the knee, hip, shoulder: in 40 percent of sufferers, arthritis develops in the larger joints. The hips in particular are often affected in young people. In addition to severe pain, movement restrictions occur.
  • Enthesitis (inflammation of the tendon insertion): This is the main feature of ankylosing spondylitis. These are inflammations in the attachment area of tendons and ligaments. Practically all patients are affected, especially as the inflammation in the spinal column also involves inflammation at the attachment of the anterior longitudinal ligament to the vertebral bodies. Around 70% of patients have enthesitis in the peripheral region, with inflammation in the heel area being very typical.
  • Iridocyclitis (uveitis): Up to 50 percent of sufferers repeatedly suffer from inflammation of the eyes. In addition to redness, sensitivity to light and pain, vision can suffer.
  • Intestine: An inflammatory infestation of the intestine can make itself felt through diarrhea and abdominal pain. Crohn’s disease is related to classic inflammatory bowel diseases (Crohn’s disease and ulcerative colitis).
  • Internal organs: In extremely rare cases, the kidneys, lungs or heart can also be affected.

What the symptoms have in common is that mild impairments are usually followed by a deterioration. If the pain was only on one side (constant or alternating), it will be on both sides. The severity of the movement restriction in particular varies greatly. In some cases, the inflammation of the spine leads to fusion of the vertebrae at the edges. If left untreated, the posture of sufferers changes in a characteristic way: The forward curve in the lumbar region disappears, the gluteal muscles atrophy and the backward curve in the thoracic vertebrae increases. This results in a typical massive postural defect with a hunched back, which nowadays – thanks to advances in diagnosis and treatment – rarely occurs.

Ankylosing spondylitis: diagnosis at the USZ

Due to the gradual and initially unspecific course of the disease in the early phase, ankylosing spondylitis can often remain undetected for years. Although back pain is a leading symptom, it is indicative of a variety of other illnesses and is also often a consequence of modern everyday life in otherwise completely healthy people. Rheumatoid factors do not play a role in the diagnosis, so we have to resort to other methods:

  • Medical history: Among other things, we analyze existing back pain in terms of timing, dependence on rest or movement, occurrence during the day or at night.
  • Physical examination: We measure and test the mobility of the spine, for example by bending, stooping, twisting and tilting. We also palpate joints and tendon insertions for swelling or pain.
  • Mennell test: While the patient is lying on their side, we press one hand against the buttocks at the level of the sacrum and stretch the sacroiliac joint by simultaneously lifting one thigh. If this method causes pain even at low pressure, inflammation can be inferred as a sign of ankylosing spondylitis.
  • Magnetic resonance imaging (MRI): In contrast to ossifications, which are already visible in the late phase on X-rays, the MRI examination allows the inflammation in the bone and in the attachment area of the tendons and ligaments, as well as in the joints, to be visualized. However, the inflammation in the MRI should only be interpreted in conjunction with the other findings.
  • X-ray: The increasing inflammation and subsequent ossification of joint areas can be clearly seen on a classic X-ray. In the later course of the disease, the typical shape of the vertebral bodies changes to a so-called box vertebra with bony braces between the vertebrae and finally a bamboo rod spine.
  • Ultrasound: Various ultrasound procedures can also be used to detect inflammation in joints or in the tendon attachment area.
  • Blood values: The erythrocyte sedimentation rate and the C-reactive protein are two values that – if elevated – indicate inflammation in the body. However, these are elevated in at most half of those affected. The detection of the hereditary trait HLA-B27 is also informative. It should be noted that ankylosing spondylitis may still be present even if there are no signs of inflammation and a non-HLA-B27 carrier.

Ankylosing spondylitis: prevention, early detection, prognosis

The causes of ankylosing spondylitis have not been conclusively clarified, but a major influence of genes is certain in any case. Prevention in the classical sense is therefore not possible. However, the disease often progresses with mild symptoms anyway and therefore often remains undetected. A healthy diet and plenty of exercise are important.

If you are suffering from initial, possibly only diffuse symptoms, a medical examination can clarify whether you have ankylosing spondylitis at an early stage.

Progression and prognosis of ankylosing spondylitis

The course of ankylosing spondylitis is very varied and ranges from occasional pain with slight movement restrictions to major damage, such as a hump. In some cases, the main symptom is pain, in others increasing stiffness. The number of unreported cases is probably very high. As the symptoms often remain so mild that the person affected does not seek medical advice.

Around 90 percent of patients still live completely independently a good 40 years after diagnosis. Only in rare, severe cases does a hip joint have to be replaced at a young age, for example. In the later stages of the disease, osteoporosis can occur, which greatly increases the risk of fractures and further complicates the situation. There are also sufferers with severe eye, intestinal or heart complaints. Fortunately, modern medicine can prevent such a critical condition. The relapsing nature of the disease can lead those affected to become careless in their prevention. A long and good quality of life should therefore be the motivation for your consistent therapy, even in periods without symptoms.

Self-help groups

The exchange with people who are affected by the same disease can be a great support in coping with the disease. Advice on finding a suitable self-help group is available from Selbsthilfe Zürich. Self-Help Zurich and the University Hospital Zurich are cooperation partners in the national project “Health literacy thanks to self-help-friendly hospitals”.

Bechterew's disease: Treatment

There is currently no cure for ankylosing spondylitis. By taking various measures, the patient and the doctor can work together to achieve a favorable prognosis, enabling a largely symptom-free, mobile life.