25th February 2025

Spondyloarthritis

Overview of spondyloarthropathies

These are a heterogeneous group of seronegative inflammatory conditions, with common features including inflammation of the axial (spine) and peripheral joints, enthesitis (inflammation of tissue attaching ligaments and tendons to bone), a link to HLA-B27 and responsiveness to NSAIDs.

They include:

• Axial spondyloarthritis – ankylosing spondylitis (AS) when there is radiographic ankylosis (joint fusion)
• Psoriatic arthritis (PsA)
• Reactive arthritis
• Enteropathic (inflammatory bowel disease) arthritis

They typically affect patients under 45, often with a delay in diagnosis. AS affects men twice as often, while the others have equal sex distribution. The prevalence of AS may be up to 0.23% in Caucasian populations, PsA in up to 10% with psoriasis and enteropathic arthritis in up to 15% with IBD. Some with PsA never get psoriasis.

Reactive arthritis occurs in up to 4% 1-4 weeks after certain gastrointestinal and genitourinary infections, including Chlamydia, Campylobacter, Salmonella, Shigella and Yersinia. The synovitis is sterile, so distinct from septic arthritis.

Up to 95% with AS and 30% with enteropathic arthritis have HLA-B27, which carries a 5 times higher risk of reactive arthritis. It may cause abnormal T-cell responses, interplaying with abnormal environmental exposure to microorganisms (through the skin in psoriasis and bowel in IBD).

AS and PsA are progressive, though can be relapsing and remitting. Reactive arthritis is of acute onset, with 70% recovering in 6 months. Enteropathic arthritis can improve with IBD remission.

Signs and symptoms of spondyloarthropathies

These include:

• Inflammatory back pain with features of:
  • Chronic or recurrent pain >3 months
  • Morning stiffness relieved with exercise and NSAIDs
  • Pain at night
  • Buttock pain
  • Reduction in spinal mobility due to fusion
• Synovitis, usually affecting the asymmetric larger joints in the lower limbs (hips and knees)
• Enthesitis, most commonly causing Achilles tendonitis and plantar fasciitis
  • In AS this can occur at the costochondral joints with pain and reduced chest expansion
• Dactylitis, with swelling of fingers and toes

AS classically has more axial features, and the other spondyloarthropathies have more peripheral features.

PsA in particular, has a number of different patterns; alongside spine-predominant, enthesopathic-predominant, and asymmetric arthritis are also:

• Symmetrical polyarthritis
• DIPJ (distal interphalangeal joint)-predominant disease
• Arthritis mutilans in 5% with erosive arthropathy of the hands (‘telescope fingers’)

Other features are:

• Systemic fatigue, weight loss, low-grade fever, anaemia
• Non-musculoskeletal features (Table 1)

Table 1 Non-musculoskeletal features of spondyloarthritides

* The classic triad of post-infection arthritis, urethritis and conjunctivitis (‘Reiter’s syndrome’) is only seen in a minority.

General complications can include osteoporosis, fractures, nerve root entrapment and renal involvement from NSAID use.

Investigation of spondyloarthropathies

Bloods will often show a raised ESR and CRP, but negative RF and ACCP (anti-citrullinated protein) antibodies.

In reactive arthritis genitourinary and stool cultures should be taken, but are often negative.

Imaging may include:

• Pelvic (AP) and spinal X-rays showing sacroiliitis with sclerosis and erosions. Persistent sacroiliitis and enthesitis cause bony growth with syndesmophytes (spurs) and intervertebral ligament calcification. There is eventual ankylosis (fusion) of the sacroiliac and spinal facet joints (‘bamboo spine’).
• MRI can show sacroiliitis not seen on X-ray.
• Hands and feet X-rays in PsA, which may show erosion of the DIPJs (‘pencil-in-cup appearance’) with periarticular bone formation.

Box 1 Distinguishing spondyloarthropathies from rheumatoid arthritis

Management of spondyloarthropathies

First-line therapy involves NSAIDs. These can be contraindicated in IBD and sometimes cause rebound skin symptoms in psoriasis. Alongside this are analgesia adjuncts, physiotherapy and smoking cessation. Corticosteroid injections are recommended for localised inflammation.

If there is poor response of peripheral disease or severe symptoms, second-line treatment may involve the DMARDs sulfasalazine or methotrexate. Leflunomide and ciclosporin are sometimes used in PsA.

With poor response to the above or severe axial symptoms, the biological DMARD TNF-α (tumour necrosis factor) inhibitors can be considered (adalimumab, infliximab, etanercept, golimumab). NICE has also licensed Ustekinumab, an IL-23 inhibitor, in PsA for non-responders.

Management of cardiovascular comorbidities is important.

References

• Chan A, Sacks S. Ankylosing spondylitis [Internet]. BMJ Best Practice. BMJ Publishing Group; 2022 [cited 2022 July 25]. Available from: https://bestpractice.bmj.com/topics/en-gb/366
• Michet C. Psoriatic arthritis [Internet]. BMJ Best Practice. BMJ Publishing Group; 2022 [cited 2022 July 25]. Available from: https://bestpractice.bmj.com/topics/en-gb/524
• Carter J. Reactive arthritis [Internet]. BMJ Best Practice. BMJ Publishing Group; 2022 [cited 2022 July 25]. Available from: https://bestpractice.bmj.com/topics/en-gb/597
• National Institute for Health and Care Excellence. Ankylosing spondylitis [Internet]. NICE. 2019 [cited 2022 July 27]. Available from: https://cks.nice.org.uk/topics/ankylosing-spondylitis/
• National Institute for Health and Care Excellence. Psoriasis [Internet]. NICE. 2022 [cited 2022 July 27]. Available from: https://cks.nice.org.uk/topics/psoriasis/
• Clunie, Gavin and others (eds), Oxford Handbook of Rheumatology, 4 edn, Oxford Medical Handbooks (Oxford, 2018; Oxford Academic, 1 July 2018)
• Kumar, P. J., & Clark, M. L. (2002). Kumar & Clark clinical medicine. Edinburgh, Saunders