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Axial spondyloarthritis is a chronic and progressive inflammatory arthropathy. Axial refers to the axial portion of the skeleton, with spondylo meaning vertebra in Greek.
Comprehensive overview of axial spondyloarthritis, its genetics, symptoms, diagnosis, and treatment options by Rhesus Medicine.
Key Takeaways
- Axial spondyloarthritis is a genetically influenced chronic inflammatory disease primarily affecting the spine and sacroiliac joints.
- Early diagnosis using clinical criteria, genetic markers, and imaging is crucial to prevent severe spinal deformities and disability.
- NSAIDs are first-line treatment, with biologics reserved for refractory cases to control inflammation and prevent progression.
- Extra-articular symptoms and comorbidities require multidisciplinary management to address systemic involvement.
- Lifestyle modifications, including exercise and smoking cessation, are important adjuncts to pharmacological therapy.
Summary
- Axial spondyloarthritis is a chronic inflammatory arthritis affecting the axial skeleton, with ankylosing spondylitis being its radiographic form.
- It has a strong genetic component, with 97% heritability and a significant association with the HLA-B27 gene and ERAP1 gene.
- Symptoms typically include inflammatory back pain with gradual onset before age 40, morning stiffness, and improvement with activity.
- Diagnosis involves clinical criteria (ASAS), genetic testing for HLA-B27, and imaging such as X-rays and MRI to detect sacroiliitis and spinal changes.
- Characteristic imaging findings include vertebral squaring, syndesmophytes, ligamentous calcification, and the bamboo spine appearance.
- Extra-articular manifestations occur in 25% of cases, including anterior uveitis, cardiovascular issues, neurological complications, and links to psoriasis and inflammatory bowel disease.
- Treatment focuses on pain reduction, maintaining mobility, and preventing complications, starting with NSAIDs and progressing to biologics if needed.
- Nonpharmacological management includes tailored physiotherapy, postural training, exercise, and smoking cessation to reduce respiratory and cardiovascular risks.
- Diagnostic delay averages 8 years, highlighting the need for increased awareness and early intervention.
- Corticosteroids are generally not used long-term but may be applied intra-articularly or topically for specific symptoms like uveitis.
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Speaker A
It is a form of spondyloarthropathy alongside psoriatic arthritis, reactive arthritis, and enteropathic arthritis, with each of these having an overlap in clinical features and an association with the HLA-B27 gene.
Speaker A
When radiographic evidence is visible in the spine or sacroiliac joints, it is termed ankylosing spondylitis, with ankylosing meaning fusing or stiffening.
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Otherwise, it is termed non-radiographic axial spondyloarthritis. It is thought to be heavily genetically determined, with 97% heritability, which is a measure of how much a condition is affected by genetics.
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The HLA-B27 allele is seen in around 90% of cases but is estimated to contribute around 20% of the genetic risk.
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ERAP1 is a gene coding for an aminopeptidase involved in antigen presentation and processing and is thought to have significant contribution.
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The exact mechanism, however, remains unclear, though it does involve inflammation, cartilage erosion, and subsequent repair in the form of ossification.
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It is this ossification that leads to the typical calcification of the annulus fibrosis and syndesmophyte formation, meaning the bony growths that develop in the ligaments around the spine.
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Eventually, leading to fusion of vertebrae and the bamboo spine appearance. Inflammation begins at the bone cartilage interface and features mononuclear infiltration and an increased number of osteoclasts.
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It is most commonly seen between the ages of 20 and 40 and is around three times more common in males than females and 10 times more likely in those with a first-degree relative.
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It is also fairly under-diagnosed, with a diagnostic delay of around 8 years. The most common symptom is back pain, classically referred to as inflammatory back pain, featuring a gradual onset at 40 years or younger, morning stiffness, typically lasting above 30 minutes,
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improvement with activity, nocturnal disturbance often in the second half of the night, and a total duration of symptoms of 3 months or more before seeking medical attention.
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There may also be paraspinal spasms. And left untreated, axial spondyloarthritis can form kyphosis, meaning an excessive forward rounding curvature of the upper spine, which can become fixed, resulting in the inability to lie flat and compromises respiratory function.
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Systemic or extra-articular features are seen in 25% of cases, which can include anterior uveitis, which can often be recurrent, cardiovascular, such as aortic insufficiency, pericarditis, and conduction abnormalities, neurological, such as sciatica or nerve compression, and there is also a risk of
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cauda equina syndrome. Up to 30% of patients have been noted to have a non-specific colitis, and there is a link with inflammatory bowel disease.
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Respiratory manifestations include shortness of breath, cough, and hemoptysis, meaning coughing up of blood, which can result from fibrosis and cavitation, which could become infected, for example, with aspergillus.
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Psoriasis is also linked. Lab investigations can include a blood test looking for the presence of the HLA-B27 allele.
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And lumbosacral x-ray or MRI can be done, with MRI showing changes earlier and may be done if the initial x-ray is normal. Early changes on x-ray of the sacroiliac joints include subchondral erosions, sclerosis, and eventually fusion, with findings being mostly
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symmetrical. Early changes in the spine can include vertebral squaring with sclerosis, called the shiny corner sign, with later changes featuring prominent syndesmophytes, which, as we said, are bony or calcific outgrowths in the spinal ligaments or annulus fibrosis.
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Diffuse ligamentous calcification and osteoporosis, overall giving a bamboo spine appearance. Overall, these are combined using criteria. The Assessment of Spondyloarthritis International Society ASAS diagnostic criteria being most commonly used.
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To fulfill the criteria, patients must have back pain for more than 3 months beginning at an age before 45, as well as either HLA-B27 plus at least two separate spondyloarthritis features, which include dactylitis, enthesitis of the heel, history of inflammatory back pain,
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arthritis, psoriasis, inflammatory bowel disease, or uveitis, or a family history of spondyloarthritis, elevated C-reactive protein, or a good response to nonsteroidal anti-inflammatory drugs.
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The criteria can also be met by radiographic or MRI evidence of sacroiliitis plus at least one spondyloarthritis feature.
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Treatment goals involve reducing pain, maintaining range of motion, and preventing end organ damage. With most patients having minimal disability, though in some cases can be progressive and severe.
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Nonsteroidal anti-inflammatory drugs are first line, such as naproxen or ibuprofen, with European guidelines recommending a trial with the largest tolerable doses within maximum dose ranges. Daily dosing is used in those with active condition, though there is conflicting evidence if
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continuous dosing reduces the risk of progression, and proton pump inhibitors are often co-prescribed to reduce the risk of gastrointestinal complications.
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Analgesia like codeine and paracetamol can be added to help control pain. If two different nonsteroidals fail, we move on to alternatives. These can include tissue necrosis factor alpha inhibitors like adalimumab, infliximab, or etanercept, as well as anti-interleukin 17 monoclonal antibodies like
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secukinumab if ineffective. Janus kinase inhibitors, such as tofacitinib, can be used but are usually reserved for those not responding to above therapies.
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Corticosteroids are not indicated long term, though may be used intra-articularly or, in the case of anterior uveitis, topically.
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Nonpharmacological management includes daily exercise, which may involve postural training, especially training extensor muscles that oppose the direction of potentially deforming flexors.
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And in general, physiotherapy can vary in terms of its intensity, duration, and frequency, being tailored to the individual.
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Smoking is discouraged due to the potential respiratory involvement, as well as due to these patients having a higher cardiovascular disease risk, which is why traditional risk factors like diabetes and hypertension should also be addressed.
Topics:axial spondyloarthritisankylosing spondylitisHLA-B27inflammatory back painsacroiliitisNSAIDsbiologicsbamboo spineERAP1rheumatology
