What is psoriatic arthritis?
Psoriatic arthritis (PsA) is a form of arthritis affecting individuals with psoriasis.
- Joints become inflamed, which causes pain, swelling and stiffness.
- Tendons may also become inflamed and cause pain (such as tennis elbow and pain around the heel).
- Joints are typically stiff after resting, particularly early in the morning or in the evening.
- Approximately 10% to 20% of those with psoriasis may develop some form of arthritis.
- In most people (80%) the arthritis develops after the appearance of psoriasis.
- Some people may develop a condition (uveitis) of the eye which may cause redness and inflammation (if you are concerned about this seek medical advice).
- People with psoriatic arthritis often complain of feeling fatigued or exhausted.
- There is some evidence that people with psoriasis and/or psoriatic arthritis might have a slightly increased cardiovascular risk (heart disease). See Psoriasis and the Heart
How do joints and tendons become inflamed?
Joints normally function to allow movement to occur between bones. In the joint the end of the bone is covered with cartilage, around which is a capsule lined
by a membrane called synovium.
This membrane normally makes the fluid that lubricates the joint space , allowing movement. In arthritis the synovial membrane becomes inflamed and releases substances that cause inflammation.
The inflamed synovium releases more fluid than normal and so the joint becomes tender and swollen. Persistent inflammation may lead to damage to the cartilage and erosion of the underlying bone.
Synovial membrane also lines and lubricates tendons and so they also become inflamed.
What is different about psoriatic arthritis?
There are several features that distinguish psoriatic arthritis from other forms of arthritis:
- The pattern of joints that may be involved is different.
- Psoriatic arthritis may just affect a small number of joints (oligoarthritis) or many joints (polyarthritis). Most commonly the psoriatic arthritis is asymmetric in pattern (unlike rheumatoid arthritis which is symmetrical).
- Psoriatic arthritis may affect the end joints of fingers; often corresponding with the fingers that have psoriatic nail involvement. See Nail Psoriasis.
- When psoriatic arthritis affects the joints of the spine and sacroiliac joints it is called spondylitis (similar to ankylosing spondylitis). This can result in stiffness and pain of the back or neck.
- An entire toe or finger can become swollen or inflamed (dactylitis).
- Some people have involvement of the jaw.
- Psoriatic arthritis may affect where the tendons connect to the bone (enthesitis). Common areas to be affected include the heel and ankle.
- Psoriatic arthritis may cause joints to become stiff and limit the amount of movement in them. In some severe cases the joint may fuse so it cannot be moved.
- Importantly, the absence of rheumatoid factor in the blood helps distinguish psoriatic arthritis from rheumatoid arthritis.
Distinguishing features are not always present and the individual may have swelling of a few or many joints, similar to other types of arthritis, making diagnosis difficult.
At what age and who does psoriatic arthritis affect?
- It may come on at any age.
- Although well recognised it is uncommon in children.
- Usually (in 80% to 90% of cases) the psoriatic arthritis comes on after the psoriasis.
- Men and women are equally affected.
- 60% of men will develop arthritis of the spine as opposed to 40% of women.
What is the outlook in psoriatic arthritis?
- Although psoriatic arthritis cannot be cured at present, many effective treatments exist.
- Treatments will depend on the severity of the disease, with some individuals having minimal arthritis while others are more severely affected.
- Psoriatic arthritis is a chronic condition that may wax and wane.
- Early diagnosis is essential in order to identify those who may develop more severe psoriatic arthritis and commence treat ment that can prevent damage occurring to the joints.
- Only a small minority of individuals will go on to develop severe and widespread joint damage.
- Joints that are initially involved in psoriatic arthritis are usually the ones that continue to cause the problems at a later stage, though this is not always the case.
- Genetic markers to identify individuals with potentially more severe arthritis are now becoming practical and will help in reflecting the most suitable type of treatment.
What is the treatment for psoriatic arthritis?
- Although psoriatic arthritis is a chronic condition with no cure, there are many effective treatments to manage and control it. Some treatments, but not all, for psoriatic arthritis also help psoriasis of the skin. See our What is Psoriasis? for further information.
- Your psoriatic arthritis is likely to be managed by a number of healthcare professionals which may include:
- your general practitioner (GP)
- a rheumatologist (joint specialist)
- a dermatologist (skin specialist)
- a specialist nurse
- a physiotherapist
- an occupational therapist
- a podiatrist (foot care)
- an ophthalmologist (eye specialist)
- a surgeon (joint replacement).
You may also be referred for specialist tests and imagery, which may include when appropriate x-rays, magnetic resonance imaging (MRI), ultrasound etc.
- Depending on your individual circumstances you may be offered some of the following different types of treatments:
- Topical analgesic creams for the treatment of mild to moderate pain caused by arthritis.
- Topical medications for skin psoriasis such as vitamin D derivatives, although they may help the skin, have not been shown to benefit joints.
- NSAIDs (non-steroidal anti-inflammatory drugs) work by blocking the production of some of the body’s chemicals that cause inflammation and pain.
- DMARDs (disease-modifying anti-rheumatic drugs) are often prescribed in addition to NSAIDs to help slow down the biological processes that cause the persistent inflammation.
- Corticosteroids as joint injections can be very effective, although these do not work equally well in all individuals. They are safe when used in moderation and with precision.
- Biologics (such as anti-TNF drugs) are a newer group of drugs that may be offered if you do not respond effectively to other DMARDs. They act by mimicking the effects of substances naturally made in the human immune system.
- Medical advice is vital about medications that can control inflammation and joint damage.
- A severely inflamed joint should be treated with a period of rest followed by exercise (under medical supervision). Physiotherapy of joints and muscles which have stiffened can help prevent loss of movement. See Physiotherapy & Exercise: Psoriatic Arthritis.
Remember: All treatments may have unwanted side effects or require special precautions (eg during pregnancy). Always make sure you have all the information before embarking on any course of therapy; this includes reading the Patient Information Leaflets (PIL) provided with your medicines.
Does diet make a difference?
- No particular diet has shown to be uniformly effective; some people with psoriatic arthritis have found cutting down on saturated fats helps and may reduce the doses needed of other treatments, though research has not confirmed this.
- Dietary supplements such as evening primrose oil and certain fish oils may have a variable effect too, but are safe and have other health benefits, but beneficial effects have not been proven in research.
- Following guidelines about healthy lifestyle, keeping weight down and moderating intake of alcohol are all generally accepted as beneficial regardless of having psoriasis or psoriatic arthritis.
Remember: many so-called cures for arthritis are not proven by clinical trials to be of use and may be driven by profit to those advocating them.
Does climate make a difference?
- Ultraviolet light helps psoriasis in some cases, otherwise climatic conditions such as the weather have a minor role to play; those whose skin and joints wax and wane together are usually better in summer than winter.
Does the severity of skin or nail psoriasis matter?
- In 80% of individuals with psoriatic arthritis, nail changes are found compared with only 40% in those with psoriasis alone.
- Nail changes include pitting and discolouration of the nail due to abnormalities in the growth of tissue in the nail bed.
- The risk of developing psoriatic arthritis is greater in individuals with severe psoriasis, yet severe psoriatic arthritis may occur with minimal skin disease.
Do we know what causes psoriatic arthritis?
- The cause of psoriatic arthritis is the subject of much research.
- You cannot catch psoriatic arthritis or psoriasis from someone else. Therefore they are not contagious.
- The cause of psoriatic arthritis is not proven but experts believe it to be a combination of genetic, immunological and environmental factors. 40% of people with psoriasis or psoriatic arthritis have a firstdegree relative with the condition. This means you have a higher chance of developing psoriasis or psoriatic arthritis if you have a relative who has the condition. Some experts believe infections such as streptococcal infections may provoke the psoriatic arthritis though this is not proven.
- Trauma and stress may be contributing factors, although not proven.
- The genetic make-up of an individual is likely to determine the risk of developing psoriasis and psoriatic arthritis and probably influence the severity.
- There are certain genetic markers linked to the immune system which are now being used to predict the severity of psoriatic arthritis.
- Much more is known about the mechanisms that lead to inflammation in other conditions and it is likely advances in science will lead to much more effective treatments with fewer side effects.
This article is adapted from the What is Psoriatic Arthritis? leaflet.
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