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Extra-articular Manifestations of Ankylosing Spondylitis

by Roberto Russo

Recently I have been involved in the development of an education program for GP’s regarding Rheumatoid arthritis and one issue that had stimulated discussion was the data regarding extra-articular manifestations (EAMs). In a bygone era, prior to the early use of Disease Modifying Anti-Rheumatic Drugs (DMARDs), EAMs were definitely more common. However, with the current approach of introducing DMARD therapy early there has seen a reduction in the frequency of these consequent conditions. These include entities such as scleritis (inflammation of the lining of the eye), pleuritis (inflammation of the lining of the lungs), and Felty’s syndrome (a combination of Rheumatoid arthritis, enlargement of the spleen, and a reduction in the number of neutrophil, specific type of white blood cells important in immune defence). Nevertheless, we Rheumatologists continue to ask our Rheumatoid arthritis patients for any symptoms that may indicate the presence of these conditions.

Acute Anterior Uveitis Image accessed on 11th April 2014 at http://lifeinthefastlane.com/uveitis/

Acute Anterior Uveitis Image accessed on 11th April 2014 at http://lifeinthefastlane.com/uveitis/

Therefore, it was with interest that I read a recent article on the epidemiology of EAMs in another common rheumatic disease, Ankyolising Spondylitis. Ankylosing Spondylitis is a chronic inflammatory disease with an estimated prevalence in western populations of about 0.6%. It is characterized by inflammation of the spine and not infrequently of peripheral joints; however, multiple other organ systems can become affected by the disease process. The most common sites include the eye, bowel, and skin. At these sites the disease manifests as acute anterior uveitis (AAU), inflammatory bowel disease (IBD), and psoriasis. The presence of these EAMs is of relevance because they impact upon the patient’s quality of life and upon our treatment decision.

 

Stolwijk et al1 found;

  1. AS patients were 2 to 20 times more likely to develop these diseases compared to the normal population.
    1. Men were more likely than women to either develop an EAM or have one present at diagnosis
    2. However, the prevalence of EAMs decreased with age, except for psoriasis where age was not a factor
  2. A significant proportion of these EAMs were present prior to the date of AS diagnosis
    1. 12% had AAU (0.5% in controls)
    2. 5% had Psoriasis (2.5% in controls)
    3. 4% had IBD (0.6% in controls)
  3. The likelihood of developing an EAM continued over time, such that 20 year cumulative risk increased to;
    1. 24% for AAU
    2. 10% for Psoriasis
    3. 7.5% for IBD
  4. The risk of developing an EAM was highest in the 1st year after diagnosis of AS
    1. Risk dropped to baseline levels after 5 years for Psoriasis and 10 years for IBD.

The difference in the findings of this recent study compared to Rheumatoid arthritis suggest that the incidence and prevalence of these common EAMs in AS have remained stable when compared to previous cohorts.

Psoriasis Image accessed on 11th April 2014 at http://www.daavlin.com/patients/skin-conditions/psoriasis-treatment/

Psoriasis Image accessed on 11th April 2014 at http://www.daavlin.com/patients/skin-conditions/psoriasis-treatment/

A possible explanation for this may be that the time to diagnosis of AS remains prolonged in comparison to RA and there continues to be a delay in the time to commencing treatments that may alter the natural history of the disease. However, interestingly, the prevalence of these EAMs is seen to a similar degree in those who have non-radiographic axial spondyloarthritis (ie. in those where spondylitis is present without evidence of radiographic joint damage, which is considered to be a precursor to the diagnosis of AS, termed Axial Spondyloarthritis (axial SpA)), suggesting that in a proportion of patients with inflammatory spinal disease the phenotype includes inflammation at those target tissues.

This relatively high frequency of EAMs can actually be of clinical relevance in the diagnosis of inflammatory spinal diseases in those presenting with chronic low back pain. It is common practice for Rheumatologists to enquire for symptoms of these EAMs, whereby a history of AAU is strongly suspicious for SpA in those with chronic back pain (Likelihood ratio (LR) of 13.9). The presence of psoriasis and IBD in those chronic low back are also suggestive of SpA, albeit to a lesser degree (LR of 3.8 and 4.3 respectively). Finally, the results of the study also remind us to continue to vigilantly observe for the development of these conditions in those with an established diagnosis.

I wonder if you have ever been prompted to consider an inflammatory spinal disease in a patient you’ve been treating for chronic low back pain on the basis of one of the conditions discussed above. I would be most interested to hear whether it proved to be Axial Spondyloarthritis/AS and what has been the outcome since the change in the approach to treatment. Please send me any feedback or questions to Roberto@bjchealth.com.au or feel free to contact me on 0401032604 to discuss any of the topic discussed.

Reference:
  1. Stolwijk C, Essers I, van Tubergen A, et al. The Epidemiology of Extra-articular Manifestations in Ankylosing Spondyloarthritis: A population-based matched cohort study. Annals of Rheumatic Diseases, 2014: published online March 21. DOI: 10.1136/annrheumdis-2014-205253