Spondyloarthritides (aka spondyarthritis, SpA, seronegative spondylarthropathy) – these are inflammatory joint diseases of the vertebral column and sacro-iliac joints.
These conditions tend to mimic rheumatoid conditions
(e.g. rheumatoid arthritis
), but are serologically different, as rheumatoid factor is usually negative.
There is a very strong correlation between these conditions and the MHC class I: HLA-B27.
- However, it is important to remember that 5-10% of the population have this variant, and most people have no problems with it!
Epidemiology & Aetiology
- Aetiology is essentially unknown
- Associated with HLA-B27
- Sometimes associated with other disorders – such as crohn’s idsease, UC, chlamydial urethritis, psoriasis.
- There is often a lot of overlap of symptoms with psoriasis
Ankylosing Spondylitis (AS)
This is the main disorder of this category. It is relatively uncommon and 90% of cases are associated with HLA-B27. Of these, 1-2% have full blown AS, and up to 15% have some symptoms of AS.
- The prevalence of AS varies between races. HLA-B27 is particularly common in caucasians, but uncommon in black Africans, and Japanese.
- Spondylitis – inflammation of the spine
- Spondylosis – degenerative osteoarthritis changes
- Ankylosis – stiffness in a joint
- Prevalence of 1 in 1000 middle aged men
- M:F is 2:1
- But men tend to present earlier – at age 16, the M:F is 6:1
- The disease is also often milder in women
Inflammation first occurs around the enthesis – this is the site where ligaments attach to bone. As the inflammation heals, there is new bone formation in the ligament, as sclerosis of the underlying bone. (NB – sclerosis is thickening or hardening)
Eventually, there may be fusion of the vertebral bodies – which prevents flexion and rotation. This is particularly disabling when it occurs in the vertebral spine. Some patients will develop fixed spinal deformities. This is sometimes referred to as bamboo spine. Also, in sever, late disease, the posture of a patient with AS may be referred to as question mark posture – as the neck becomes hyperextended, and there is severe kyphosis of the thoracic spine. This can make forward vision difficult.
The earliest changes are usually in the sacro-iliac joints.
Usually begin before the age of 30.
- Episodic Pain! – usually in the buttocks and/or lower back in the late teenage years or early 20’s in the first sign. The pain is usually:
- Worse in the morning
- Relieved by exercise
- Diagnosis often missed due to lack of symptoms between episodes
- Retention of lumbar lordosis in spinal flexion
- Paraspinal muscle wasting (occurs later)
- Spinal stiffness – can be measured with Schoeber’s test:
- Measure 10cm above the dimples of venus with the patient stood upright. Place a dot here. As the patient to flex forward (touch their toes). Then re-measure the gap with the patient in this position. Normally, the gap should increase to >15cm.
- You may get costo-vertebral joint involvement – which can cause reduced chest expansion and anterior chest pain.
- No radiological abnormalities in early stages
Systemic manifestations / associations