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
- Peripheral osteoarthritis – 30% of patients. Pathologically the same as osteoarthritis, but has an unusual distribution. Usually the hands are spared, but the lower limbs and shoulder joints are particularly badly affected.
- Uveitis – inflammation of the inner parts of the eye. Usually in this case, anterior parts of the eye, including the iris and ciliary body.
- Cutaneous lesions – that are identical to pustular psoriasis
- Aortic incompetence (in 1-2% of cases of AS)
- Inflammatory bowel disease (Crohn’s, UC)
Examining for AS
- In the early stages of the disease, you may be able to elicit pain by pressing on the lower portion of the sacrum, whilst the patient is laid flat, face down.
- Schoeber’s Test
- Bloods – ESR and CRP are usually raised
- HLA testing – not really much use due to high incidence of HLA-B27 in normal population
X-Ray – usually normal in early disease. Later signs may include:
- Sacroiliac joint margins lose definition – as they have become eroded and sclerotic.
- Blurring of upper and lower rims of vertebrae – particularly in thoracolumbar junction. This is best seen on a Lateral X-ray
- Syndesmophytes – these are boney lesions in the enthesis, as a result of enthesitis. They tend to be vertically orientated, and not beak-shaped, unlike osteophytes (seen in spondylosis), and also the disc is preserved (again, unlike spondylosis)
- Joint fusion – may be seen in late disease. Sacroiliac, and costovertebral (reducing chest expansion), and intervertebral.
The basic treatmentis exercise! – this reduces long-term disability and other problems.
- Early diagnosis is important – this allows the regimen of exercises to be implemented early. Spinal exercises should be performed in the morning.
- Without exercise, there are wasted paraspinal muscles, and irreversible kyphosis.
During an inflammatory episode, stiffness and pain may prevent exercise. During these episodes, you may want to use an NSAID – often a long acting one, given at night helps to reduce pain, help sleeping, and aid exercise the next morning.
- Peripheral arthritis is managed with NSAID’s or local steroid injections.
- TNF-α therapy is useful in severe disease, and can reduce inflammation. But the inflammation will return as soon as treatment is stopped.
With early diagnosis, and good exercise compliance, prognosis is very good. Up to 80% of patients remain well enough to stay in full time employment. There may be general long-term back stiffness, but disability is rare.
Apart from the HLA-B27, there is no direct risk of passing on AS. Thus children with an HLA-B27 positive parent, have a 50% chance having the variant themselves, and then are at the same risk as any other person with this variant of having AS (15% chance of some symptoms, 1-2% chance of full diagnosed AS)