Ankylosing spondylitis

Background

• Chronic and progressive form of seronegative arthritis
• Inflammatory disorder of articular and para-articular entheses (where ligaments tendons and capsule meet bone)
• Axial skeleton, particularly sacroiliac joints (SIJ) and facet joints of vertebrae
• May involve greater trochanter, patella, calcaneum, iritis/uveitis and pulmonary involvement

Clinical

• M : F = 5:1, 15 - 35 yo, 90% have HLA-B27
• Back pain/stiffness (morning pain > 30 min), sciatica, wt loss, and low-grade pyrexia
• Neck and costochondral stiffness later
• Early signs
  • loss lateral flexion lumbar spine, SIJ tenderness
  • no loss of lumbar lordosis in lumbar flexion
• Check for cardiovascular (aortic incompetence/pancarditis) and pulmonary fibrosis
• Associated inflam. bowel disease
• Associated uveitis (20%), prostatitis, conjunctivitis
• Later: Bamboo spine, Amyloidosis

Differential diagnosis

• Psoriasis, Reiter's disease, enteropathic arthropathy, hyperparathyroidism, rheumatoid arthritis, gout
• Diffuse idiopathic skeletal hyperostosis (DISH)
  • Similar x-ray appearance but DISH age group is older, SIJ not involved in DISH

Investigations

• Raised ESR, positive HLA-B27, anaemia of chronic disease, rheumatoid F negative

Treatment

• NSAIDS, sulfasalazine, physiotherapy to maintain flexibility
• Infliximab / Etanercepts (anti-TNF) agentsvery effective and disease modifying especially if used early