Clinical features of axial spondyloarthritis
Inflammation in axial spondyloarthritis is centred in the axial skeleton/spine (spondylitis). It initially affects the sacroiliac joints (sacroiliitis), before involving other areas of the spine (usually progressing from the lumbar spine to the thoracic and cervical spine). Sacroiliitis manifests as stiffness and pain in the buttock, sometimes radiating into the thigh. Alternating buttock pain is characteristic.
Enthesitis (inflammation at the sites of tendon and ligament attachment to bone) is a hallmark of the disease. Dactylitis (inflammation of a whole finger or toe) and extra-articular features may also occur.
Characteristic features of inflammatory back pain associated with axial spondyloarthritis include:
- a gradual onset before the age of 45 years
- symptoms lasting longer than 3 months
- night pain and prolonged morning stiffness
- improvement with physical activity or exercise, and failure to improve with rest
- response to nonsteroidal anti-inflammatory drugs (NSAIDs).
Following inflammation and ossification of the axial entheses, the spine progressively stiffens (ankylosis). Involvement of the costovertebral joints leads to reduced chest expansion. With time, abnormal posture and impaired function may occur. Spinal osteoporosis is common; suspect fracture in patients with longstanding disease and a sudden increase in spinal pain.
Peripheral enthesitis and peripheral arthritis occur less commonly. In axial spondyloarthritis, peripheral enthesitis usually affects the heels (see Achilles tendinitis and plantar fasciitis) and the peripheral arthritis is usually oligoarticular, asymmetrical and predominantly affects the lower limbs. Arthritis of the hips and shoulder joints (including the acromioclavicular and sternoclavicular joints) occurs in some patients and can be disabling. Arthritis of the costochondral joints of the chest wall can occur and may be associated with more severe disease.
The following features are predictive of poor prognosis in axial spondyloarthritis:
- hip involvement
- age younger than 16 years at the onset of symptoms
- presence of 3 of the following factors within 2 years of the onset of symptoms:
- erythrocyte sedimentation rate (ESR) greater than 30 mm/hour or serum C-reactive protein (CRP) concentration greater than 6 mg/L
- limitation of spinal movement
- dactylitis (inflammation of a whole finger or toe)
- peripheral oligoarthritis
- inadequate symptom relief from nonsteroidal anti-inflammatory drugs (NSAIDs).
The most common extra-articular feature of axial spondyloarthritis is acute anterior uveitis, which is experienced at some point by over 15% of patients with nonradiographic axial spondyloarthritis and up to 30% of patients with ankylosing spondylitisde Winter, 2016. Advise patients to seek medical advice immediately if they experience sudden onset of unilateral eye pain, photophobia and increased lacrimation. Conjunctival injection around the rim of the iris is a characteristic finding. Urgently refer any patient with suspected acute anterior uveitis to an ophthalmologist. Treatment involves corticosteroid eye drops and mydriatics to reduce inflammation and prevent sequelae such as synechiae.
Clinical features of inflammation may also be found in other organs, including the skin and digestive tract. Less common extra-articular features of axial spondyloarthritis include aortic insufficiency secondary to aortitis, cardiac conduction defects, and apical pulmonary fibrosis.