Psoriatic arthritis
Reproduced from Issue 106 of Arthritis Today
Dr Philip Helliwell
Controversial playwright Dennis Potter brought attention to this previously little-heard of condition. Dr Philip Helliwell, senior lecturer in rheumatology at the University of Leeds, looks at its history and current treatments.
Readers of the article on paleopathology in the April edition of Arthritis Today will know that arthritis has been around for a long time. One hundred years ago the distinction between different forms of arthritis was seldom made – it was all lumped together and mostly called gout!
Then in 1896, a French physician called Bazin wrote of an association between psoriasis and arthritis. For some time this link was forgotten, but in the late 1950s a young Harrogate rheumatologist called Verna Wright developed a further interest. He was on his way to America for two years so he asked the hospital matron to keep a record of all patients admitted to the spa hospital with psoriasis. On his return he had a large group of people, including many families with this disorder, and he went on to write many papers on the clinical manifestations and familial trends of psoriatic arthritis.
Dennis Potter, psoriatic arthritis sufferer
So what makes psoriatic arthritis different to other forms of arthritis? Well, it can look just like rheumatoid arthritis, but certain features make the distinction. Firstly, inflammation is found at the "entheses,"(the places where ligaments attach to bones, such as the Achilles tendon at the heel) around the heel, knee and pelvis. Secondly, the finding of "sausage" digits – where entire fingers or toes become swollen and may resemble a chipolata. Thirdly, osteolysis – literally melting bones resulting in a floppy finger or toe. Fourthly, inflammation oin the joints at the ends of the fingers adjacent to the nails – especially if the nail is involved with psoriasis. Lastly, spondylitis – of the ankylosing kind, often less severe than ankylosing spondylitis occurring alone.
Of course, it is sometimes difficult to distinguish between psoriatic and rheumatoid arthritis. Not everyone with psoriasis and arthritis has psoriatic. If rheumatoid factor antibodies are present in this blood this helps but more advanced tests such as magnetic imaging (MRI) may be helpful. MRI enables us to look at the different sites of inflammation (such as the entheses) and can show very early changes. In fact, MRI scans are seldom done routinely, partly because of the cost and partly because the differences are usually clinically obvious.
The link between the skin and joint disease has not been fully explained. Genes are likely to be important although no clear pattern has emerged. Some doctors believe that bacteria in the skin lesions can sensitise the joints to inflammation – again no firm answers yet. Most people develop psoriasis before the arthritis but a few (fewer than 20%) experience the arthritis first or simultaneously. People in whom skin and joint disease starts at the same time often experience simultaneous flares of the two conditions.
How common are these conditions?
Psoriasis occurs in about 1–2% of the general population. About 7–15% of people with psoriasis also suffer from an inflammatory arthritis. This is high compared to people without psoriasis in whom an inflammatory arthritis is found in 1–2%. Conversely, if we take all people who have arthritis, psoriasis is found in 3–5%. The link between these conditions is clear but the processes by which the link occurs are still not certain.
What sort of treatments are available?
In general, the treatments suitable for psoriatic arthritis are very similar to those used to treat other inflammatory arthritis. Anti-inflammatory drugs (such as ibuprofen, diclofenac and naproxen) act by reducing inflammation in the lining of the joints and in entheses. They can be very effective in controlling the pain and stiffness of any form of arthritis.
Disease-modifying drugs (such as sulphasalazine and methotrexate) help by attacking the causes of the inflammation. These drugs act quite differently from anti-inflammatory drugs and hopefully will stop the arthritis from getting worse. Often these drugs will help both the skin and the joint disorders – this is especially true for methotrexate.
Many diets are suggested for psoriatic arthritis but none have been found to be very effective. Cod liver oil and other marine fish oils may reduce the amount of anti-inflammatory drugs required to control joint and skin inflammation – they act directly on the chemicals producing inflammation and not as lubricants for the joint. Sunlight and other forms of ultra-violet radiation often improve the psoriasis but may not be beneficial for the skin except in those few people in whom the skin and joint disease vary together.
Current treatment developments for rheumatoid arthritis are also likely to be of help in psoriatic arthritis. These developments include the new COX-2 anti-inflammatory drugs and the new disease-modifying drugs such as lefluminide. The use of biological treatments such as genetically engineered monoclonal antibodies which seem to be so effective in rheumatoid arthritis may also be on benefit in psoriatic arthritis. The prohibitive costs are likely to fall in time. Further research studies on the link between joint and skin disease may, in time, produce other treatment possibilities.
Psoriatic arthritis can cause severe joint damage ranking alongside rheumatoid arthritis as a major cause of disability. Hospital-based management involves all professional members of the team including physiotherapists and specialist nurses. There is a thriving patient organisation called the Psoriatic Arthropathy Alliance which produces a helpful newsletter and organises an annual conference. The concept of psoriatic arthritis as a unique condition has certainly progressed rapidly since the pioneering work of Verna Wright and the next few years should see new developments in both the cause of treatment of this condition.
Useful address:
Psoriatic Arthropathy Alliance,
PO Box 111,
St Albans,
Herts,
AL2 3JQ
