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Plaque psoriasis

Published by Bupa's health information team, August 2008.

This factsheet is for people who have plaque psoriasis, or who would like information about it.

Psoriasis is a common skin condition causing patches of inflamed skin. Plaque psoriasis is the most common type of psoriasis. It is characterised by pinkish-red scaly plaques (patches), especially on areas such as your knees and elbows.

About plaque psoriasis
Symptoms of plaque psoriasis
Complications of plaque psoriasis
Causes of plaque psoriasis
Diagnosis of plaque psoriasis
Treatment of plaque psoriasis
Further information
Questions and answers
Related topics
Sources

About plaque psoriasis

In psoriasis, the rate at which your skin is replaced is rapidly increased.

Your skin is constantly shedding old cells and being replaced with new ones from underneath, in a cycle that usually takes about 28 days. In psoriasis, this process speeds up, only taking about three to four days. New skin cells move rapidly to the surface before they have properly matured, and accumulate on the surface of the skin, forming thick patches called plaques. There is also a build-up of a type of white blood cell (called T-cells) under the skin, which causes inflammation.

Plaque psoriasis is a chronic condition. A chronic illness is one that lasts a long time, sometimes for the rest of the affected person's life. Although most people who get plaque psoriasis will have the condition for the rest of their life, about 80 percent will get remissions (periods when the symptoms decrease).

Symptoms of plaque psoriasis

The plaques in plaque psoriasis are usually pinkish-red and disc shaped, with well-defined clear edges. They will be covered with silvery white scales. They may be itchy, and sometimes, may bleed. The plaques are not contagious.

Plaque psoriasis can affect any area of your body, but it is most common to get plaques on your:

knees
elbows
scalp
hairline
lower back

You may also notice changes in your nails, such as:

irregular pitting (the surface of the nail is covered in small pin pricks)
areas of discolouration
your nail may come away from the underlying nail bed

If you think you have any of these symptoms, you should see your GP.

Complications of plaque psoriasis

Up to 10 percent of people with psoriasis also develop associated arthritis (inflamed joints). This is called psoriatic arthritis. Usually the joints at the end of the fingers and toes are affected, although the back, knees and hips may be affected too. For more information on psoriatic arthritis, please see related topics.

Anyone with psoriasis is potentially at risk of developing a more severe form of the condition, such as pustular or erythrodermic psoriasis (see related topics), although this is rare.

Your psoriasis can also become unstable. This means that you start to develop new plaques and your plaques become bigger, losing their clear-cut edges and sometimes even joining up. In unstable psoriasis, the creams and ointments that you usually use to treat your plaques may start to make your psoriasis even worse. However, it is important that you seek the advice of your doctor before changing your treatment.

Causes of plaque psoriasis

It is thought that substances produced by your immune system cause your skin to start producing new cells faster in psoriasis, as well as causing the build-up of T-cells. But what makes the immune system act like this isn't clear.

You are more likely to get psoriasis if you have a family history of the condition. If one of your parents has psoriasis, you have a one in four chance of getting it. In many people, however, there is no obvious cause.

If you have psoriasis, certain factors can cause new lesions to develop. These include:

rubbing or scratching your skin - this can cause new plaques at the area where your skin has been damaged and is called the Köbner phenomenon
infection
certain medicines (such as beta blockers and non-steroidal anti-inflammatory drugs)
alcohol
stress
smoking
sunlight (sunlight usually improves psoriasis, but in some people it can make it worse)

Diagnosis of plaque psoriasis

Your GP will ask about your symptoms and examine you. He or she may also ask you about your medical history.

Usually, your GP will be able to tell whether you have psoriasis just by looking at the areas of affected skin. He or she will assess the extent of your psoriasis and how severe it is.

If your psoriasis is extensive or severe, if it's affecting your education or work, or if your diagnosis is uncertain, your GP may refer you to a dermatologist (a doctor specialising in conditions affecting the skin).

Treatment of plaque psoriasis

There is no cure for psoriasis, but a lot can be done to help control your symptoms. Your GP will discuss your treatment options with you. It is possible that you may decide you don't need any treatment at all for your psoriasis.

Self-help

Cutting down on alcohol and smoking may help to reduce your symptoms.

Your GP will probably advise you to use emollients. He or she will usually prescribe these, but you can also buy these products from a shop without a prescription. They are very effective at keeping your skin moist, softening scaling and reducing irritation. It's worth discussing the choice of treatment with your doctor so that you can get the best results.

Topical therapies

Your GP can also prescribe a medicated topical preparation (a treatment that is applied directly to your skin, such as a cream or ointment). These are usually the first type of treatment tried. Topical treatments for plaque psoriasis include creams and ointments containing:

tar - these can reduce inflammation and scaling, and are often used in psoriasis affecting the scalp; however, they can be messy
steroids - these are often used for localised psoriasis (eg patches on your elbows or knees), but may not be used if your psoriasis is quite widespread; stronger steroids can be used on your palms and soles, or your scalp
vitamin D derivatives (such as calcitriol or tacalcitol) - these can be easier to use than some of the other products, but sometimes irritate the skin
vitamin A derivatives (such as tazarotene) - these can also irritate the skin; in addition, they should not be used if you are pregnant or plan to try for a baby
dithranol - this is usually very effective, but is also more difficult to use as it stains skin and clothes - dithranol is usually only used for a limited period and on individual, large plaques
a keratolytic agent (eg salicylic acid) - your doctor may suggest you use this if you have a lot of scaling, to reduce the scaling before beginning other treatments
tacrolimus - this suppresses the immune cells involved in causing the inflammation of psoriasis; tacrolimus ointment can be effective for plaques on sensitive areas of skin, such as the face

Light therapy

Light therapy can only be given by a dermatologist in a hospital. Your dermatologist may recommend light therapy if the above treatments haven't worked. Light therapy includes the following.

Ultraviolet B (UVB) light therapy. UVB light occurs naturally in sunlight. This therapy involves shining artificial UVB light onto your skin. You will usually have the therapy two to three times a week for several weeks.
Psoralen and ultraviolet A light treatment (also called PUVA). This involves combining a medicine which sensitises the skin to sunlight (psoralen) with a controlled dose of ultraviolet A (UVA) light. You may have psoralen as a tablet or applied directly to your skin. The UVA light is given in a machine that looks similar to a shower cabinet, containing fluorescent tubes. You usually have the treatment twice a week, for several weeks.

Oral medicines

Your dermatologist may prescribe you one of the following medicines if topical treatments and light therapy haven't controlled your symptoms; your psoriasis is extensive; or if you have psoriatic arthritis:

methotrexate
acitretin
ciclosporin
hydroxycarbamide

You take these medicines by mouth, and they work by suppressing your immune system, or by slowing down the production of skin cells.

If you are a woman, you will be warned not to become pregnant while taking these medicines or for some time afterwards. Men may also be advised they shouldn't get their partner pregnant for some time after taking some of the medicines. This is because they can cause serious damage to an unborn baby.

Biological agents

Biological agents are newer treatments for psoriasis that can be very effective, but tend to be restricted to people with severe psoriasis. They are given as an injection into your skin, or through a drip into a vein in your arm.

Your dermatologist can discuss these treatments with you. You will need to have various pre-treatment tests before you can try these medicines, and will be monitored with blood tests while you are receiving the treatment.

Further information

The Psoriasis Association
0845 676 0076
www.psoriasis-association.org.uk