The risk of developing uveitis, psoriasis and inflammatory bowel disease is increased in patients with ankylosing spondylitis.
Ankylosing spondylitis is a chronic inflammatory disease that affects around 0.6% of people in western countries. It mainly involves the spine and large joints, but may be associated with other diseases, such as psoriasis (a skin disease), inflammatory bowel disease and uveitis (an inflammation in the eye). These non-articular symptoms are known as extra-articular manifestations and they may arise from the same underlying causes, typically inflammation in the body.
WHAT DID THE AUTHORS HOPE TO FIND?
The authors hoped to learn more about extra-articular manifestations in patients with ankylosing spondylitis, such as how many patients have one or more manifestation, and whether it is possible to work out when the manifestations develop in relation to the onset of joint symptoms. If we know, for example, that the manifestations develop before the start of the joint symptoms, it may be possible to diagnose patients with ankylosing spondylitis sooner. The authors also wanted to find out the increased risk of developing uveitis, psoriasis or inflammatory bowel disease in patients with ankylosing spondylitis, compared to controls (healthy people) without ankylosing spondylitis.
WHO WAS STUDIED?
A large general practitioner (GP) database from the United Kingdom was used to identify patients with ankylosing spondylitis. These patients were matched with control subjects from the same database without ankylosing spondylitis, in order to compare the frequency of uveitis, psoriasis and inflammatory bowel disease between the two groups. All persons were over the age of 16. Overall there were 4101 patients with ankylosing spondylitis included, and 28,591 controls.
HOW WAS THE STUDY CONDUCTED?
All patients with a diagnosis of ankylosing spondylitis between 1987 and 2012 were identified. These patients were matched with persons without ankylosing spondylitis, based on age, gender and practice. Both in patients with ankylosing spondylitis, and in controls without ankylosing spondylitis, the frequency of a diagnosis of uveitis, psoriasis and inflammatory bowel disease were checked. In this way it was possible to calculate how often patients developed uveitis, psoriasis and inflammatory bowel disease, both in patients with ankylosing spondylitis and in controls without ankylosing spondylitis, and how early these manifestations occurred compared to the onset of their ankylosing spondylitis.
WHAT WERE THE MAIN FINDINGS OF THE STUDY?
The authors found that the prevalence of uveitis was significantly associated with disease duration – with 12% of patients having uveitis at diagnosis of ankylosing spondylitis and 25% having the condition after 20 years. In other words, patients with ankylosing spondylitis may develop a first episode of uveitis many years after the diagnosis of ankylosing spondylitis. The risk of developing an episode of uveitis was more than 15-times higher in patients with ankylosing spondylitis compared with controls. This risk was highest in younger patients (16–39 years), in males and in patients with early disease.
Psoriasis was identified in 4% of patients at diagnosis of ankylosing spondylitis, and this proportion increased to 10% after 20 years. Compared with controls, the risk of psoriasis was 1.5 times higher, although this risk decreased over time.
Inflammatory bowel disease was present in 4% of patients at the diagnosis of ankylosing spondylitis, increasing to 8% after 20 years of ankylosing spondylitis. Compared with the general population, the risk of developing inflammatory bowel disease was 3-times higher, but was only significantly increased in the first ten years of follow-up from ankylosing spondylitis diagnosis.
ARE THESE FINDINGS NEW?
Yes – this study is the first to show the frequency and risk of developing uveitis, psoriasis and inflammatory bowel disease in patients with ankylosing spondylitis in relation to the time of diagnosis and when compared to the general population.
HOW RELIABLE ARE THE FINDINGS?
The main limitation is that there may be a bias in the diagnosis of ankylosing spondylitis, uveitis, psoriasis and inflammatory bowel disease. Although it is thought that the accuracy of diagnoses in the database used is high, there may be misclassification. There is also often a delay in the diagnosis of ankylosing spondylitis, so it is not always possible to measure how far from disease onset the extra-articular manifestations have occurred.
Additionally, this study was conducted in the United Kingdom, and the picture may not be the same in other countries and regions of the world.
WHAT DO THE AUTHORS PLAN ON DOING WITH THIS INFORMATION?
The authors are reversing the study and looking at how often joint symptoms occur in patients with uveitis, psoriasis and inflammatory bowel disease. They are also conducting studies to measure how having uveitis, psoriasis and inflammatory bowel disease affects disease outcomes – such as quality of life and the ability to work.
WHAT DOES THIS MEAN FOR ME?
The results suggest that patients with ankylosing spondylitis have a higher risk of developing uveitis, psoriasis and inflammatory bowel disease. It is important to be aware of this and to talk to your doctor if you have ankylosing spondylitis and think you may have developed an extra-articular manifestation, particularly uveitis which requires immediate medical treatment.
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Date summary prepared: July 2015
Summary based on research article published on: 21 March 2014
From: Stolwijk, C. et al. The epidemiology of extra-articular manifestations in ankylosing spondylitis: a population-based matched cohort study. Ann Rheum Dis 2015;74:1373–8. doi:10.1136/annrheumdis-2014- 205253
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