What is ankylosing spondylitis?

What is ankylosing spondylitis?

Ankylosing spondylitis is a chronic disease that affects the sacroiliac and spinal joints, causing pain and stiffness and making mobility difficult. Your diagnosis can be delayed between one and three years.

It is a chronic inflammatory disease that affects the joints, especially the sacroiliac joints and the spine, although it can also affect other peripheral joints. Spondylitis causes the vertebrae to fuse and stiffen (hence its name), making it difficult or preventing the affected joints’ mobility. This happens in approximately 30% of cases and especially in patients with highly advanced disease.

Its main clinical manifestations are pain and stiffness, which can initially be attributed to other causes. Over the years, the persistence and worsening of these symptoms lead to the diagnosis. A pain that should attract attention because it differs from classic low back pain improves with rest, unlike in spondylitis.

It is much more common in men, but the incidence is increasing in women, affecting people of all races equally. Contrary to what you might think when talking about joint diseases, ankylosing spondylitis is more common in young people and usually appears between 20 and 30 years; even in 10% of patients, the initial symptoms appear before the age of 16 years.

Its prevalence is estimated at around 1% of the population, with an approximate incidence of 1 to 7 cases per 100,000 inhabitants per year. In Spain, for example, it represents some 500,000 affected individuals.

Its fundamental importance is given by the functional limitation, therefore, in the quality of life of the individual who suffers it, causing high health costs for the medical care they require. In up to 20% of cases, it can lead to permanent disability, as it is a cause of chronic low back pain in young adults.

In recent years, biological therapy has been a real advance, not only for the control of symptoms in patients with poor response to conventional treatments but also for managing non-articular symptoms and associated cardiovascular risk.

Causes of ankylosing spondylitis

The causes of ankylosing spondylitis are unknown, although it appears to be closely related to the HLA-B27 antigen, a protein found on the surface of white blood cells. Up to 90% of patients with ankylosing spondylitis have this protein in their blood. But this does not mean that this antigen’s presence necessarily implies that the disease will be suffered.

The role this protein plays in the development of the disease is still under study. However, it seems that its greater expression in these patients makes them more susceptible to other agents, such as microorganisms, causing the inflammation that underlies spondylitis.

There is also an increased concordance of twin spondylitis, suggesting a highly probable genetic predisposition. Specifically, it is estimated that the risk of suffering from the disease with HLA B27 + and a first-degree relative with ankylosing spondylitis is 20%. However, this is the only hypothesis, as it is unknown for sure what causes ankylosing spondylitis.

Some factors such as obesity or tobacco consumption can contribute to a worse evolution of this process, although without absolute evidence of being part of the causes.

Zahir Singh Barad

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