Psoriasis

What is psoriasis?

Psoriasis is a common skin condition which typically causes patches ('plaques') of red, scaly skin to develop. The severity varies greatly. In some cases it is mild with a few small patches being barely noticeable. In others there are patches of varying size all over the body. In many cases it is somewhere between these two extremes.

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. It is not uncommon to have long spells without the rash. However, in some cases the flare-ups occur often.

Who gets psoriasis?

About 2 in 100 people develop psoriasis at some stage. It has a tendency to run in families. It can first develop at any age, but it most commonly starts between the ages of 15 and 25.

What causes psoriasis?

The exact cause is not known. Normal skin is made up of layers of skin cells. The top layer of cells 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 (described below).

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.

Aggravating factors

There is no apparent reason why most flare-ups of psoriasis develop. However, in some cases psoriasis is more likely to flare up in certain situations. These include the following:

• Stress. It is impossible to measure stress, or prove that it can cause flare-ups of psoriasis. However, some people feel that stress does contribute on some occasions.
• 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 (see below).
• Medication. Medicines such as beta-blockers (propranolol, atenolol etc), chloroquine, lithium, anti-inflammatory pain killers (ibuprofen, naproxen, diclofenac, etc), and alcohol sometimes trigger a flare-up of psoriasis. In some cases the psoriasis does not develop until the medication has been taken for weeks or months.

What are the different types of psoriasis?

Plaque psoriasis
This is the most common form. The rash is made up of patches on the skin called plaques. 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 the front of the elbows and knees, the scalp, and the lower back. However, plaques may appear anywhere on the skin, but they are uncommon on the face.

The extent of the rash varies between cases, 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 near each other merge to form large plaques.

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 in the nails. Sometimes the nail separates from the nail bed. There is no effective treatment for the nail problems of psoriasis.

Scalp psoriasis
This can occur alone, or in combination with psoriasis in other parts of the body. It looks like severe dandruff.

Guttate ('drop') psoriasis
This typically occurs following a sore throat which is caused by a bacterium. 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.

Other
Other kinds of psoriasis such as pustular psoriasis or 'erythroderma' are uncommon.

Other problems of psoriasis

Psoriasis can be itchy, but does not usually cause much discomfort. It is not infectious. About 1 in 10 people with psoriasis also develop inflammation and pains in some joints (arthritis). This is called psoriatic arthropathy. The cause of this is not clear.

The main problem for many people is the unsightly appearance of the rash. Some people become quite anxious or depressed about their psoriasis.

What are the common treatments for psoriasis?

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

There are various creams and ointments 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 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. Some people do not want any treatment if the rash is not too bad, or not in a noticeable place.

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. Do not be afraid to ask a doctor or nurse if you are unsure. The following are commonly used treatments.

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 very 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). They can cause irritation in some people and should not be used on the face. There is also a scalp preparation of calcipotriol.

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. There are various brands and types. Traditional tar preparations are messy to use, but modern formulas are more pleasant. Tar based shampoos are popular for scalp psoriasis. You should not use tar on the face, or on any broken or sore skin.

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 it 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.

There are various types of dithranol preparations. 'Short contact therapy' is popular. This involves putting a higher strength dithranol 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 sometimes prescribed for short periods for areas of skin with thick plaques. Ideally, they should not be used for more than 4-6 weeks at a time. This is because the skin may become used to or 'tolerant' to steroids if used longer. Side-effects with long term use may also occur. They are easy to use and may be a good treatment for difficult areas such as the scalp and face. Steroid lotions are useful for flare-ups of scalp psoriasis.

Tazarotene
This is another cream that is sometimes used. 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 sometimes 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.

Combinations
Sometimes treatments are 'rotated'. For example, a steroid ointment may be advised for up to 6 weeks, and then replaced with dithranol cream for a while. 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 sunlight, 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 powerful medicines which can suppress inflammation are sometimes used. For example, methotrexate and cyclosporin. 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

The Psoriasis Association, 7 Milton Street, Northampton, NN2 7JG
Tel: 0845 676 0076    Web: www.psoriasis-association.org.uk

Psoriatic Arthropathy Alliance, PO Box 111, St Albans, Herts, AL2 3JQ
Tel: 0870 70 32 12    Web: www.paalliance.org