This term describes a family of diseases with common features which are summarized. The major members of the family are shown which emphasizes the overlap of features between the different syndromes. There is a common genetic basis to these conditions:
HLA-B27 is found in all of them but more frequently in classical ankylosing spondylitis with sacroiliitis and a bamboo spine on X-ray than in other syndromes. The same patient may have several different syndromes from the group either simultaneously or at different times: thus a patient with enteropathic synovitis may also have anterior uveitis. Similarly, the same conditions may occur within families, e.g. patients with reactive arthritis may have uncles and aunts with psoriasis or nephews and nieces with juvenile arthritis. In some cases it is impossible to describe the condition of a particular patient except as an ‘undifferentiated spondylarthropathy’.
The tendency to develop these conditions is inherited but there is increasing interest in the role of gut inflammation in precipitating the development of the various clinical features. It is well known that gut or venereal infections precipitate reactive arthritis, but recent studies show that gut inflammation is often present in ankylosing spondylitis and other spondylarthropathies. It is thought that microbial antigens are disseminated from the gut to, for example, joints where, as in the gut, they cause lymphocyte activation, cytokine production and inflammation.
Ankylosing spondylitis is the most important cause of inflammatory back pain. It affects young adults, with men more severely afflicted than women. It presents with back pain and morning stiffness, and is typically associated with sacroiliitis on X-ray. Other important associations include peripheral arthritis and non-articular features such as iritis.
It is a genetically determined disease, susceptibility to which is related to the presence of HLA-B27. This antigen is found in about 5% of European people and 95% of patients with ankylosing spondylitis. Studies of large populations of B27-positive subjects such as blood donors suggest that about 20% of B27-positive individuals have ankylosing spondylitis or a related disease. The prevalence of ankylosing spondylitis in the population can thus be calculated as 1%. Since HLA-B27 is found equally in men and women, the incidence of the disease should also be equal. Population surveys using radiological sacroiliitis as the main criterion for diagnosis have shown both a much lower incidence than 1% and a male preponderance. It is now clear that there are many mild cases, especially in women, that present as pain and stiffness but with no other features. The disease is probably almost as common in women as in men and the presence of X-ray changes are not essential to the diagnosis. The frequency of ankylosing spondylitis in different populations is roughly paralleled by the incidence of HLA-B27: Africans and Japanese have a low incidence of both HLA-B27 and ankylosing spondylitis. Some native American tribes have a correspondingly higher incidence of both.
The typical case presents with an insidious onset of low back pain in the late teens or early twenties. The pain is typically inflammatory in type. The first symptoms may arise from sacroiliitis, with pain in the buttocks radiating down the back of both legs. Peripheral polyarthritis may also occur; the joints of the lower limbs are particularly affected. Plan tar fascii tis may cause heel pain. Iritis occurs at some time in 30% of cases. Inspection of the spine in a patient with ankylosing spondylitis reveals two characteristic abnormalities:
1 Loss of lumbar lordosis and increased kyphosis
2 Variable limitation of spinal flexion and a reduction in chest expansion. In addition, tenderness is commonly found around the
pelvis and chest wall.
THE E SRAND C RP are often raised.
X-RAYS OF THE LUMBAR SPINE AND PELVIS are often but not always abnormal. In the early stages, the sacroiliac joints are eroded, with irregular margins, and there is sclerosis of adjacent bone. As the disease advances, the sacroiliac joints may fuse. In the spinal column, the characteristic abnormality is a syndesmophyte that grows between the margins of the vertebrae. There is calcification and ossification of the interspinous ligaments so that with the syndesmophytes, the PA X-ray shows three continuous lines, the so-called tramline appearance. Vertebrae appear square as a result of the erosion of their corners. These changes are particularly seen at the dorsolumbar junction, but may occur throughout the spine.
HLA-B27 (measured in blood lymphocytes) is useful supporting evidence in the difficult case but one must remember that many normal people carry the gene.
COURSE AND PROGNOSIS
In all but the mild case there is progressive limitation of spinal movement over the course of a few years. In severe cases the spine becomes completely fused. There is a tendency for patients to develop a kyphosis, but this can usually be prevented. Despite the limitation of spinal movement, most patients are able to lead a normal active life and remain at work. In women, the disease is usually mild, with little restriction and no deformity. In contrast to RA, the disease does not remit in pregnancy but nor does it cause problems with childbirth. It tends to improve with age but seldom resolves completely. Most cases of ankylosing spondylitis do well. Death is seldom related to the disease except in rare complications like amyloidosis and neck fractures. The disease tends to be more severe when it starts earlier: hip disease is more likely when the disease starts in teenagers; when it starts after the age of 22 years, hip replacement is almost never required. Neck problems are also more likely with a younger onset. While men are more likely to have aggressive spinal disease, women are more likely to have peripheral joint disease.
NSAIDS ARE VERY EFFECTIVE; slow-release indomethacin is often the best choice (75 mg at night). It is particularly useful in relieving night pain and morning stiffness. Useful alternatives include piroxicam or flurbiprofen.
AN EXERCISE PROGRAMME is essential to maintain movement, relieve symptoms and prevent deformity, particularly kyphosis. Exercises should be carried out at least twice daily. In addition, patients should be encouraged to take part in whatever sports they like.
SULPHASALAZINE is useful as a long-term suppressive drug in the difficult case but penicillamine and gold are not effective. Azathioprine may be useful for peripheral arthritis but not for spondylitis. Radiotherapy has been used but should seldom be necessary and carries a small risk of leukaemia. Surgery plays little part, but hip replacement is occasionally required.