Psoriasis and Arthritis

Psoriatic skin disease is a relatively common condition for which the treatments are somewhat unpleasant and not entirely effective. It is known that an arthritic syndrome is associated with this skin disorder but even then the diagnosis may be missed when patients with psoriasis present with joint signs. There are many effects from psoriatic arthritis on the joints and the arthritic damage can lead to disability and compromised quality of life. In the United Kingdom the prevalence of psoriasis itself is around 2%, with 14% of this number exhibiting some signs of involvement in their joints.

In about fifteen percent of people suffering from these conditions the arthritic symptoms start before any skin lesions are apparent and in examination of people with psoriasis abnormalities in soft tissues have been found in the absence of joint symptoms. Psoriatic arthritis tends to affect a smaller number of joints that rheumatoid arthritis although there may be a similar pattern. In many cases only one or two joints may be involved. The attachments of the tendons and ligaments to the bones, areas called entheses, are typically involved. The largest such attachment in the body is that of the Achilles tendon to the heel bone and this area is often involved in inflammation and pain.

With so many entheses in the body this might explain why some patients complain of widespread pain symptoms not be closely related to their joints. Individual joints of the fingers can swell, either on their own or with involvement of other joints, and this is a negative sign for the disease. Inflammatory back pain present with the typical features which also occur in ankylosing spondylitis. Usual symptoms are early morning stiffness, steady and gradual onset, worse pain at night, pain better with exercise and worse with resting. Back involvement may be present but not give symptoms in up to a third of patients. Inflammation of the end joints of the fingers and nail involvement may also occur.

Diagnosing joint symptoms related to psoriasis can be difficult as the population ages and people complain routinely of more and more joint symptoms. The possibility of psoriatic arthritis should however always arise when a diagnostician is consulted by a person with psoriasis who complains of joint symptoms, with particular reference to back pain of possible inflammatory origin and involved distal finger joints. Typical blood tests which are raised in the presence of inflammation in the body are the ESR (erythrocyte sedimentation rate) and the CRP (C-reactive protein). If the joint picture is suspicious but no psoriasis is easily apparent it may be important to examine the patient carefully for hidden affected areas.

Typically 30% of people diagnosed with this condition will suffer with non-progressive disease in a few affected joints. This presentation is usually effectively treated with steroid injections into the joints as required and by symptomatic management. Identifying this group initially is important to exclude those with worse disease who are likely to show increased inflammatory blood markers, to be male, to have a larger number of affected joints and to have used steroids previously. If showing these negative factors they are more likely to develop damaging disease to the joints with increased disability and a reduction in their quality of life.

Around five percent of sufferers develop a very destructive and quickly advancing form of the arthritis. Metabolic syndrome and cardiovascular disease are more prevalent and can shorten life so the risk factors such as smoking, obesity, high blood pressure and cholesterol are important to control. Presentation of any joint features in the presence of psoriasis is an indication for referral to a rheumatologist, although in some cases the symptom presentation might be widespread pain or repeated local problems such as tennis elbow. Early referral can prevent the onset of joint destructive problems and should be encouraged.

A joint damaging and fast advancing arthritic disease is present in around 5% of sufferers from psoriatic arthritis. Cardiovascular disease and metabolic syndrome are more common and affect life expectancy so it is important to identify and control risks such as cholesterol, being overweight, hypertension and smoking. Patients should be referred to a rheumatologist if they have psoriasis and any features of joint problems, remembering that some patients present with pain which is widespread or conversely which is very local such a bilateral tennis elbow. Joint protection is best provided by early referral to prevent long term damage.