Psoriatic arthritis is an inflammatory arthritis associated with the common inflammatory skin condition known as psoriasis.
Patients may have the same symptoms as rheumatoid arthritis.
The exact cause is not known.
The onset is usually between the ages of 30 and 50 years.
Psoriatic arthritis has variable severity, from mild to disabling.
An inflammatory arthritis associated with psoriasis - a chronic skin and nail disease. There are five patterns:
Arthritis involving primarily the small joints of fingers or toes
Asymmetrical arthritis, which involves joints of the extremities
Symmetrical polyarthritis, which resembles rheumatoid arthritis
Arthritis mutilans, which is rare but very destructive
Arthritis of the sacroiliac joints and spine (psoriatic spondylitis)
The prevalence of each of these forms is hard to establish and some patients may show overlapping features or even suffer from more than one type. Sometimes it is associated with inflammation in the eyes, or of the bony sites of attachment of ligaments and tendons (enthesitis). This would cause local pain, for example at the heels.
Psoriatic arthritis often manifests the same symptoms as rheumatoid arthritis and virtually all affected patients have psoriasis. The latter is characterised by thickened, inflamed patches of skin. These are often covered with silver-grey scales. About 10-25% of psoriasis sufferers have accompanying arthritis, which is characterised by pain and swelling in one or more joints.
It is not known what causes psoriatic arthritis, but an interplay of immune, genetic and environmental factors is probably present. Both psoriasis and psoriatic arthritis flare up in the presence of immunodeficiency due to HIV infection (AIDS).
Who gets it and who is at risk?
It affects men and women equally and usually starts between the ages of 30 and 50 years. However, it can begin during childhood. Of the many types of arthritis, psoriatic arthritis is relatively rare. The psoriatic component of the disease often precedes arthritis by several months or years, but in up to 15% of cases arthritis precedes the diagnosis of psoriasis.
Symptoms and signs
Symptoms of psoriasis and psoriatic arthritis include:
Scaly red patches on the scalp, elbows, knees, and/or buttocks
It may manifest as a single small patch on the scalp.
Some people will have a rash covering a good deal of the body.
Pitting and/or discoloration of fingernails and/or toenails
Pain and swelling in one or more joints, usually the last joints of the fingers or toes, the wrists, knees, or ankles
Swelling of fingers and/or toes that gives them a "sausage" appearance
Stiffness of the joints, including morning stiffness
Psoriatic arthritis can develop over a long period of time, or it can appear quite suddenly. The skin rash usually develops months to years before the joint swelling and pain. However, sometimes it can develop years after the joint symptoms have started.
Your doctor will ask you about your symptoms and perform a physical examination. Skin and nail changes are characteristic of psoriasis and must be present before a diagnosis can be made with certainty. A family history is common and should be specifically asked for by the practitioner - especially if the rash is not present and the arthritis may appear initially as a non-specific rheumatoid factor-negative arthritis.
Since the symptoms are similar to other forms of arthritis, like gout, reactive arthritis and rheumatoid arthritis, your doctor may also perform some or all of the following tests:
X-rays to look for changes in your bones and joints
Blood tests to rule out other diseases
Joint fluid tests to rule out gout, another type of arthritis that may resemble psoriatic arthritis
It is important to realise that the diagnosis remains a clinical one. It does not require X-rays or blood tests, as these can often be normal. In some cases, X-rays may reveal characteristic erosion of the bone around joints, as well as thinning of the underlying bone.
Blood tests may reveal an elevated erythrocyte sedimentation rate (ESR), and the C-Reactive protein, CRP, and help confirm non-specific inflammation. A mild anaemia, and elevated levels of blood uric acid can be seen in some sufferers.
Initial treatment of psoriatic arthritis consists of the use of nonsteroidal anti-inflammatory drugs (NSAIDs), or newer safer anti-inflammatories called COXIBs. These produce fewer stomach side effects but are contra-indicated in those with known heart disease. However, these drugs do nothing to control the underlying disease and may even cause a flare-up of the skin condition.
To address the underlying disease process, disease-modifying therapies are needed, called DMARDs. Methotrexate is the drug of choice as it fortuitously controls both the skin disease as well as the arthritis. Methotrexate is a very effective drug. However, it needs to be taken for several months under the supervision of a rheumatologist as continuous use requires monitoring of liver enzymes and blood counts. Dose adjustments to tailor the therapy to the exact profile of the patient are needed from time to time. Avoidance of alchohol and use of folic acid supplements are commonly advised while on Methotrexate.
Salazopyrine has been beneficial for some sufferers, but offers no relief of the skin condition, however. Azathioprine may be used in severe cases of the disease. A new drug, Leflunomide (Arava), developed for use in rheumatoid arthritis, has also been shown to be beneficial. Again, monitoring of liver enzymes is crucial to the safety of this medication.
Corticosteroid injections directly into the joints are used with great success and occasionally intramuscular steroids are used to control flare-ups.
New biologic therapies such as Infliximab, Etanercept and Adalimumab have been shown to offer excellent control of both joint and skin disease in resistant cases. Due to cost they are usually prescribed for those whose response to conventional DMARDs is not optimal or for those who can afford them.
The pain and swelling of arthritis can make joints stiff and hard to move. If this happens, your doctor or physical therapist will recommend special exercises to keep your joints strong and flexible. General exercise such as walking can help to improve your overall health. Proper exercise is very important.
Generally, a normal amount of rest and sleep will be enough for you. For some sufferers, psoriatic arthritis can cause extreme fatigue. More rest than usual and learning how to use your energy wisely throughout your daily activities would then be recommended.
Heat and cold treatments may help to relieve pain and reduce swelling in joints. This includes soaking in a warm tub and placing a heating pad on the affected joint.
Surgery helps sufferers who develop joint destruction and mechanical problems of the joints. It may be important to stabilse joints which have undergone severe erosive change, for example of the small finger joints.
Psoriatic arthritis is generally a mild to moderate condition and with proper treatment joint pain and stiffness can be relieved and skin problems kept under control. For some sufferers it can, however, have more serious implications that require combinations of medications to control symptoms and prevent joint damage.
As the causes are not known, there is no way to predict or prevent the disease. Swift action when it is detected can, however, secure proper treatment and relief of symptoms. With good compliance with treatment, deformity and damage can usually be prevented.
When to call a doctor
Thickened, inflamed patches of skin and joint pains and stiffness should be a clear indication to visit a physician about your condition. Discoloration of nails, the swelling of fingers, and a rash on your body should also prompt you to visit your doctor. The specialist for the condition is a rheumatologist. The problem is a medical one, not a surgical one.
Reviewed by Dr I C Louw, Rheumatologist/Physician and Dr A Halland, Rheumatologist/Physician
Reviewed by the Arthritis Foundation, September 2011