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Seronegative spondyloarthopathy

Published on 01 April 2008
Source: Arthritis Today

Dr Andrew KeatIf you have discovered that you have a spondyloarthropathy or a spondyloarthritis or a seronegative spondyloarthopathy or even a spondylothingumee, what on earth have you got? asks Dr Andrew Keat.

There is a big problem with words in the world of arthritis and rheumatic disease. The terms used to refer to various forms of arthritis are often difficult to understand, or even to say, and the area of spondyloarthropathy scores pretty highly in this respect.

Most medical terms try to describe aspects of the disorder in a way that helps make it recognisable. For example, arthritis means inflammation of the joint or joints. However, some older terms are simply hangovers from long ago when our understanding of these diseases was very different.

A bit of history

Sixty years or more ago, most forms of arthritis in which lots of joints were inflamed, were called rheumatoid arthritis. This term itself is a hangover from earlier days when a quite different disease, known as rheumatic fever, was common and chronic persistent arthritis was considered to be rather like it.

The discovery of a group of antibodies, often found in the blood or serum of patients with rheumatoid arthritis, seemed to offer some understanding of the disease. These antibodies are known as rheumatoid factors. It soon became clear that people who had arthritis and rheumatoid factor in the serum (described as being seropositive) were more likely to have what we now know as typical rheumatoid arthritis while those without the antibody (seronegative) might also have inflamed joints but with a different pattern and outlook.

Not surprisingly, several different forms of arthritis are seronegative but it was something of an advance to discover that there were at least two distinctive groups of inflammatory arthritis. Later, it was recognised that among the various forms of seronegative arthritis there is a distinctive family of disorders, in each of which inflammation of the spine may occur. Inflammation of the spine – of whatever cause – is called spondylitis.

Occasionally spondylitis is caused by infection leading to an abscess in the spine. This is infective spondylitis. However, the form of spondylitis being considered here is not infective and has to be distinguished from the infective form. Because the tendency of this kind of spondylitis is to stiffening of the joints of the spine, even to the extent of rigid fusion in some people (ankylosis), the term ankylosing spondylitis is used.

The spondyloarthropathy 'family'

Lady holding sore neckFour conditions – ankylosing spondylitis, reactive arthritis (also known as Reiter's syndrome), enteropathic arthritis associated with the bowel disorders ulcerative colitis and Crohn's disease and psoriatic arthritis associated with the skin disease psoriasis – are regarded as being members of a family of disorders. Because of the common thread of spondylitis which can occur in each of these conditions, these four disorders are known as spondyloarthopathies (sometimes abbreviated to SpA).

In fact, doctors cannot make up their minds as to whether the words should end with '-itis' which means inflammation of, or '-opathy' which means something wrong with, but for practical purposes spondyloarthropathy and spondyloarthritis are interchangeable. These are 'family names', distinct from the more specific spondylitis.

In reality, in addition to these four conditions, some people develop features which strongly suggest that their disease falls within the spondyloarthopathy family, but which do not allow a clear-cut diagnosis to be made and in this circumstance the term undifferentiated spondyloarthopathy is often used. This is particularly useful in children and young adults when it may be especially difficult to ascribe a form of arthritis precisely to one or other condition.

Although spondylitis occurs commonly in people with spondyloarthropathies by no means everyone gets it. When it is the main problem, the term ankylosing spondylitis is used. Some other medical problems particularly affect people with spondyloarthropathies.

A potentially serious inflammation of the eye – iritis or acute anterior uveitis – which are the same thing – may cause pain and redness of one eye lasting from a few days to several months and can lead to blindness. Very mild bowel inflammation – which may not cause symptoms – is also common in people with SpA. Usually this does not cause problems but in a few the bowel inflammation is severe; in this case the term enteropathic arthritis is used. An inflammatory condition of the skin and/or mouth or genitals called psoriasis may also occur in people with SpA. When psoriasis is a major feature the term psoriatic arthritis is usually used.

The cause or causes of SpA is/are not known. But it is clear that a group of inherited genes determine who is susceptible to them. Chief amongst these is a gene called HLA-B27. This is present in seven or eight per cent of healthy people but in almost everyone with ankylosing spondylitis, and – more than one would expect – in people with other SpA. A great deal is now understood about these genes though just what effect they have is still not fully known. So it is not uncommon to find someone else in the family who has one or another SpA feature though it is unusual for children of an affected parent to develop a SpA.

The spondyloarthopathy family members

Ankylosing spondylitis

Ankylosing spondylitis (AS)Man sitting at desk is an inflammatory disorder of the spine which usually starts in late teens or early twenties. Symptoms vary but most people develop pain and stiffness in the lower back and buttocks; initially discomfort is often worse at night or when inactive and it is associated with tiredness. Some people get better over a few months but, for many, pain persists with gradual restriction of movement of the back and neck. About one-third of people with AS also have arthritis at joints other than the spine, usually the hips or knees, and inflammation and pain may also occur at sites of tendon attachments especially at the heel. Episodic inflammation of the eye (iritis) may also give a particular problem. For most sufferers, AS persists life-long.

Reactive arthritis

Reactive arthritis is also often called Reiter's syndrome. This form of arthritis usually starts in early adult life but may occur at any time. It particularly affects the knees and feet but inflammation at the spinal joints, especially the sacroiliac joints, may occur either during the acute episode or later. Reactive arthritis is unusual in being triggered by an infection, usually either a diarrhoeal illness or a sexually transmitted infection.

Enteropathic arthritis

Around 10 per cent of people with the inflammatory bowel disorders ulcerative colitis or Crohn's disease also develop arthritis. This may affect any joints but often affects the feet, ankles and knees. As with other spondyloarthopathies, inflammation in the spine in general, and in the sacroiliac joints in particular, is not unusual as is inflammation of the eyes. Low-grade inflammatory bowel disease is actually quite common in people with other spondyloarthopathies though this is not usually severe enough to cause symptoms or problems.

Psoriatic arthritis

Psoriasis is a flaky skin rash that affects around five per cent of the UK population. A few people with it also develop arthritis which may vary from a relatively minor illness affecting one or two joints to a very aggressive disorder causing widespread joint damage. Some people also develop inflammation in the sacroiliac joints and spine as well as at tendon attachments such as at the heels. People with other spondyloarthopathies may also develop skin rashes which are essentially psoriasis.

Undifferentiated spondyloarthropathy

Some adults and children develop arthritis, such as a swollen knee, sometimes with other features such as iritis or heel pain, which resembles a spondyloarthopathy but doesn’t quite conform to one or other specific 'family member'. In this circumstance the condition may be designated as an undifferentiated spondyloarthopathy, provided other possible explanations have been excluded.


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