Psoriasis

What is psoriasis?

Psoriasis is a common skin condition which typically develops as patches ('plaques') of red, scaly skin. Once you develop psoriasis it tends to 'come and go' throughout life. A flare-up can occur at any time. The frequency of flare-ups varies. There may be times when the psoriasis clears for long spells. However, in some people the flare-ups occur often. Psoriasis is not due to an infection and is not infectious, nor is it cancerous.

The severity of psoriasis varies greatly. In some people it is mild with a few small patches that develop which are barely noticeable. In others, there are many patches of varying size. In many people the severity is somewhere between these two extremes.

For a list of websites that contain pictures of skin conditions including psoriasis see www.patient.co.uk/showdoc/1097/

What are the different types of psoriasis?

There are different types of psoriasis, although plaque psoriasis (described below) is by far the most common and typical type.

Plaque psoriasis

This is common. The rash is made up of patches on the skin called plaques. The picture shows a typical plaque of psoriasis next to some normal skin.

Each plaque usually looks red with overlying flaky white scales that feel rough. There is usually a sharp border between the edge of a plaque and normal skin. The most common areas affected are over elbows and knees, the scalp, and the lower back. However, plaques may appear anywhere on the skin, but they do not usually occur on the face.

The extent of the rash varies between different people, and can vary from time to time in the same person. Many people have just a few small plaques when their psoriasis flares up. Others have a more widespread rash with large plaques. Sometimes, small plaques that are near to each other merge to form large plaques.

Plaque psoriasis can be itchy, but does not usually cause too much discomfort. Treatment is discussed later.

Scalp psoriasis

This occurs in about half of people affected by plaque psoriasis. It can also occur alone without any other part of the skin being affected. It looks like severe dandruff.

Nail psoriasis

This occurs in about half the people with plaque psoriasis. It may also occur alone without the skin rash. There are pinhead sized pits (small indentations) in the nails. Sometimes, the nail becomes loose on the the nail bed.

Guttate ('drop') psoriasis

This typically occurs following a sore throat which is caused by a bacterium (germ). The plaques of psoriasis are small (less than 1 cm) but occur over many areas of the body. It normally lasts a few weeks, and then fades away. It may never return. But, if you have an episode of guttate psoriasis, you have a higher than usual chance of developing common plaque psoriasis at a later time.

Flexural psoriasis

This occurs on skin in the creases of the skin (flexures) such as in the armpit, groin, under breasts, and in skin folds. The affected skin is red and inflamed. Unlike plaque psoriasis, affected skin is smooth and does not have the rough scaling.

Pustular psoriasis

This is uncommon and mainly affects the palms of the hands and and soles of the feet. In this situation it is sometimes called palmoplantar pustulosis. Affected skin develops crops of pustules which are small fluid filled spots. The pustules of pustular psoriasis do not contain germs (bacteria) and are not infectious. The skin under and around the pustules is usually red and tender. Rarely, a form of pustular psoriasis can affect skin apart from the palms and soles. This more widespread form of pustular psoriasis is a more serious form of psoriasis and needs urgent treatment.

Erythrodermic psoriasis

This is a widespread erythema (redness) of much of the skin surface which is painful. It is rare, but is serious and needs urgent treatment as it can cause excessive protein and fluid loss that can lead to dehydration and severe illness.

What causes psoriasis?

Normal skin is made up of layers of skin cells. The top layer of cells are flattened and are gradually shed (they fall off). New cells are constantly being made underneath to replace the shed top layer. It normally takes about 28 days for a bottom cell to reach the top and to be shed.

People with psoriasis have a faster turnover of skin cells. It is not clear why this occurs. More skin cells are made which leads to a build up of cells on the top layer. These form the flaky plaques on the skin, or severe dandruff of the scalp seen in scalp psoriasis.

There is also a slight change of the blood supply of the skin. This tends to cause some inflammation in the skin. This is why the skin underneath a patch of psoriasis is usually red and inflamed.

The cause of the increased cell turnover and skin inflammation of psoriasis is not known. Genetic (hereditary) factors seem to play a part as about half of people with psoriasis have a close relative also affected. It may be that some factor in the environment (perhaps a virus) may trigger the condition to start in someone who is genetically prone to develop it. Another theory is that the immune system may be 'overreacting' in some way to cause the inflammation. Research continues to try to find the exact cause.

Who gets psoriasis?

About 2 in 100 people develop psoriasis at some stage of their life. It can first develop at any age, but it most commonly starts between the ages of 15 and 25.

One large study also found that smokers (and ex-smokers for up to 20 years after giving up) have an increased risk of developing psoriasis compared to non-smokers. One theory for this is that toxins (poisons) in cigarette smoke may affect parts of the immune system involved with psoriasis.

Aggravating factors

In most people who have psoriasis, there is no apparent reason why a flare-up develops at any given time. However, in some people, psoriasis is more likely to flare up in certain situations. These include the following:

• Stress. It is difficult to measure stress and to prove the relationship between stress and psoriasis. However, it is thought that stress can contribute to a flare up of psoriasis in some people. There is some evidence to suggest that the treatment of stress in some people with psoriasis may be of benefit.
• Infections. Psoriasis may flare up if you have a feverish illnesses. In particular, a sore throat caused by a certain type of bacterium is a cause of guttate psoriasis.
• Drugs. Some drugs and medicines may possibly trigger or worsen psoriasis in some cases. Drugs that have been suspected of doing this include: beta-blockers (propranolol, atenolol etc), chloroquine, lithium, anti-inflammatory pain killers (ibuprofen, naproxen, diclofenac, etc), ACE inhibitor drugs, and alcohol. In some cases the psoriasis may not flare up until the medication has been taken for weeks or months.
• Smoking. As mentioned, smoking may help to initially trigger psoriasis to develop in some cases. Toxins from cigarette smoke may also aggravate existing psoriasis.
• Trauma. Injury to the skin, including excessive scratching, may trigger a patch of psoriasis to develop. The development of psoriatic plaques at a site of injury is known as the Koebner reaction.
• Sunlight. Most people with psoriasis say that sunlight seems to help ease their psoriasis. Many people find that their psoriasis is less troublesome in the summer months. However, some people notice the opposite with strong sunlight seeming to make their psoriasis worse. A severe sunburn (which is a skin injury) can also lead to a flare up of psoriasis.
• Hormone changes. Psoriasis in women tends to be worst during puberty and during the menopause. These are times when there are some major changes in female hormone levels. Some pregnant women with psoriasis find that their symptoms improve when they are pregnant, but it may flare up in the months just after having a baby. Again, this is thought to be related to changes in hormone levels.

Joint problems

About 1 in 10 people with psoriasis also develop inflammation and pains in some joints (arthritis). This is called psoriatic arthritis. Any joint can be affected, but it most commonly affects the joints of the fingers and toes. The cause of this is not clear. See separate leaflet called 'Psoriatic Arthritis' for details.

How is psoriasis diagnosed?

Psoriasis is usually diagnosed by the typical appearance of the rash. The rash is often very typical, and no tests are usually needed. Occasionally, a biopsy (small sample) of skin is taken to be looked at under the microscope if there is doubt about the diagnosis.

What are the common treatments for plaque and scalp psoriasis?

There is no once-and-for-all cure for psoriasis. Treatment aims to clear the rash as much as possible. However, as psoriasis tends to flare up from time-to-time, you may need courses of treatment 'on and off' throughout your life.

There are various treatments that are used to treat psoriasis. There is no 'best buy' that suits everybody. The treatment advised by your doctor may depend on the severity, site, and the type of psoriasis. Also, one treatment may work well in one person, but not in another. It is not unusual to try a different treatment if the first one does not work so well.

Many of the treatments are creams or ointments. As a rule, you have to apply creams or ointments correctly for best results. It usually takes several weeks of treatment to clear plaques of psoriasis. Make sure you know exactly how to use whatever treatment is prescribed. For example, some preparations should not be used on the skin creases (flexures), on the face or on broken skin, and some should not be used if you are pregnant. Do ask a doctor, nurse or pharmacist if you are unsure as to how to use your treatment, and for how long.

The following is a brief overview of the more commonly used treatments for plaque and scalp psoriasis. Treatments of the less common forms of psoriasis are similar, but are not dealt with here. Your doctor will advise.

Not treating may be an option

Many people have a few patches of psoriasis that are not too bad or not in a noticeable place. In this situation, some people do not want any treatment. If you opt for no treatment, you can always change your mind at a later time if the rash changes or gets worse.

Moisturisers (emollients)

These are not 'active' treatments but help to soften hard skin and plaques. They may reduce scaling and itch. There are many different brands of moisturiser creams and ointments. A moisturiser may be all that you need for mild psoriasis. You can also use one in addition to any other treatment, as often as needed, to keep the skin supple and moist.

Vitamin D based creams such as calcipotriol, calcitriol and tacalcitrol

These are popular and often work well to clear plaque psoriasis. They seem to work by affecting the rate of cell division in skin cells. They are easy to use, are less messy, and have less of a smell than coal tar or dithranol creams and ointments (below). However, they can cause irritation in some people. There is also a scalp preparation of calcipotriol. Note: they may not be suitable for pregnant or breast feeding women.

Coal tar preparations

These have been used to treat psoriasis for many years. It is not clear how they work. They may reduce the turnover of the skin cells. They also seem to reduce inflammation and have 'antiscaling' properties. Traditional tar preparations are messy to use, but modern formulas are more pleasant. There are various modern brands and types of creams which contain between 0.4% and 2% crude coal tar. Tar based shampoos which have a coal tar content of up to 2.5%.are popular for scalp psoriasis.

Dithranol

This has been used for many years for psoriasis. In most cases a daily application of dithranol to a psoriasis plaque will eventually cause the plaque to go. However, dithranol irritates healthy skin. Therefore, you need to apply it carefully to the psoriasis plaques only. To reduce the chance of skin irritation, it is usual to start with a low strength and move onto stronger ones gradually over a few weeks. When applying dithranol, you should protect your hands with gloves, or wash your hands thoroughly afterwards.

Dithranol preparations come in different brands and strengths. 'Short contact therapy' is popular. This involves putting a higher strength dithranol preparation on the plaques of psoriasis for 15-60 minutes each day, and then washing it off. Dithranol may stain skin, hair, clothes, bedding, baths, etc.

Steroid creams or ointments

These work by reducing inflammation. They are easy to use and may be a good treatment for difficult areas such as the scalp and face. However, one problem with steroids is that in some cases, once you stop using the cream or ointment, the psoriasis may 'rebound' back worse then it was in the first place. Also, side-effects may occur with long term use, especially with the more potent (stronger) preparations.

Therefore, if a steroid is used, a doctor may prescribe it for a limited period only (a few weeks or so, and less for a strong steroid), or on an intermittent basis. As a rule, a steroid cream or ointment should not be used regularly for more than four weeks without a review by a doctor. Steroid lotions are useful for flare-ups of scalp psoriasis.

Tazarotene

This is another cream that is sometimes used. It is a vitamin A based drug. Irritation of the normal surrounding skin is a common side-effect. This can be minimised by applying tazarotene sparingly to the plaques and avoiding normal skin.

Salicylic acid

This is often combined with other treatments such as coal tar or steroid creams. It tends to loosen and 'lift' the scales of psoriasis on the body or the scalp. Other treatments tend to work better if the scale is lifted off first by salicylic acid.

For scalp psoriasis

A tar-based shampoo is often tried first and often works well. Some preparations combine a tar shampoo with either a salicylic acid preparation, a coconut oil/salicylic acid combination ointment, a steroid preparation, calcipotriol scalp application, or more than one of these.

Combinations

Some preparations use a combination of ingredients. For example, calcipotriol combined with a steroid may be used when calcipotriol alone has not worked very well. As mentioned, it is not usually wise to use a steroid long-term. Therefore, one treatment strategy that is sometimes used is calcipotriol combined with a steroid for four weeks, alternating with calcipotriol alone for four weeks.

Other combinations such as a tar preparation and a steroid are sometimes used. Other 'rotating' treatment strategies are sometimes used. For example, a steroid for a few weeks followed by a course of dithranol treatment.

Scalp treatments often contain a combination of ingredients such as a steroid, coal tar, and salicylic acid.

Other treatments

If you have severe psoriasis then you may need hospital based treatment. Phototherapy (light therapy) is commonly used in hospitals. This may involve treatment with UVB light. Another type of phototherapy is called PUVA (Psoralen and Ultra Violet light in the A band). This involves taking tablets (psoralen) which enhances the effects of ultraviolet light on the skin, and then attending hospital for regular sessions under a special light which emits UVA.

Sometimes people with severe psoriasis are given intense courses of treatment using the creams or ointments described above, but in stronger strengths and with special dressings.

If psoriasis is severe and is not helped by the treatments listed above then a powerful medicine which can suppress inflammation is sometimes used. For example, methotrexate, ciclosporin, acitretin, infliximab, etanercept or efalizumab. There is some risk of serious side-effects with these medicines, so they are only used on the advice of a specialist.

Further information and support

Psoriasis Association

Dick Coles House, 2 Queensbridge, Bedford Road, Northampton, NN4 7BF
Tel (helpline): 0845 6 760 076
Web: www.psoriasis-association.org.uk
Founded in 1968 the Association has three fundamental aims: to support those who have psoriasis; to raise awareness about psoriasis; to fund research into the causes of and treatments for psoriasis.

PAPAA - The Psoriasis and Psoriatic Arthritis Alliance

PO Box 111, St Albans, Hertfordshire, AL2 3JQ
Tel: 0870 770 3212
Web: www.papaa.org
Provides support and information for people with psoriasis and psoriatic arthritis.