Axial Spondyloarthritis

KEY FEATURES

Essentials of Diagnosis

• Chronic low backache and stiffness in young adults (onset age < 45 years), worst in the morning

• Progressive limitation of back motion and of chest expansion

• Transient (50%) or persistent (25%) peripheral arthritis

• Anterior uveitis in 20–25%

• May be radiographic (ankylosing spondylitis) or non-radiographic

• Negative serologic tests for rheumatoid factor and anti-cyclic citrullinated peptide antibodies

• HLA-B27 testing is most helpful when there is an intermediate probability of disease

General Considerations

• Chronic inflammatory disease of the joints of the axial skeleton, manifested clinically by pain and progressive fusion of the spine

• Axial spondyloarthritis (axSpA) can be

  • Radiographic, with diagnostic changes of sacroiliac joints or spine visible on plain radiograph; radiographic axSpA has historically been called ankylosing spondylitis

  • Nonradiographic, in which axial inflammation (sacroiliitis) is only visualized by MRI

• The radiographic/nonradiographic classification more likely represents a spectrum of disease rather than distinct conditions

Demographics

• Age at onset is usually in the late teens or early 20s

• Incidence is greater in males than in females

CLINICAL FINDINGS

Symptoms and Signs

• Gradual onset with intermittent bouts of back pain that may radiate into the buttocks

• Pain is worse in the morning and associated with stiffness that lasts hours

• Pain and stiffness improve with activity, in contrast to back pain due to mechanical causes, which improves with rest and worsens with activity

• Symptoms progress in a cephalad direction

• Back motion becomes limited, with the normal lumbar curve flattened and the thoracic curvature exaggerated

• Chest expansion is often limited due to costovertebral joint involvement

• In advanced cases, the entire spine becomes fused, allowing no motion in any direction

• Acute arthritis of the peripheral joints occurs in ∼50% of cases, and permanent changes—most commonly in the hips, shoulders, and knees—are seen in ∼25%

• Enthesopathy, a hallmark of the spondyloarthropathies, can manifest as

  • Swelling of the Achilles tendon at its insertion

  • Plantar fasciitis or

  • Dactylitis

• Anterior uveitis in up to 25% of cases

Differential Diagnosis

• Low back pain from mechanical causes, disk disease, and degenerative arthritis

• Rheumatoid arthritis

  • Predominantly affects multiple, small, peripheral joints of the hands and feet

  • Usually spares the sacroiliac joints and only affects the cervical component of the spine

• Spondyloarthropathy associated with inflammatory bowel disease (IBD) causes bilateral sacroiliitis that is indistinguishable from ankylosing spondylitis

• Sacroiliitis associated with reactive arthritis and psoriasis is often asymmetric or even unilateral

• Ankylosing hyperostosis (diffuse idiopathic skeletal hyperostosis [DISH], Forestier disease)

  • Exuberant enthesophytes formation

  • Enthesophytes are thicker and more anterior than the syndesmophytes of ankylosing spondylitis

  • Sacroiliac joints are not affected

• Osteitis condensans ilii

DIAGNOSIS

Laboratory Tests

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