What is psoriasis?

Psoriasis is a common skin condition affecting 2-3% of the population of the United Kingdom and Ireland.
It is very simply a speeding up of the usual replacement processes of the skin. Normally skin cells take about 21-28 days to replace themselves; in psoriasis this process is greatly accelerated, and skin cells can be replaced every 2-6 days. This results in an accumulation of skin cells on the surface of the skin, in the form of a psoriatic plaque. This process is the same wherever it occurs on the body.

Who gets psoriasis?
Psoriasis can occur at any point in the lifespan, affecting children, teenagers, adults and older people. It affects males and females equally.

Is psoriasis catching?
Psoriasis cannot be caught from other people nor can it be transferred from one part of the body to another.

What does it look like?
Patches of psoriasis (also referred to as plaques) are raised red patches of skin, covered with silvery white scales. The silvery white scales are the accumulation of the skin cells waiting to be shed, and the redness is due to the increase in blood vessels required to support the increase in cell production. Psoriasis can range in appearance from mild to severe. The plaques can appear in a variety of shapes and sizes, varying from a few millimetres to several centimetres in diameter. Plaques of psoriasis have a well-defined edge from the surrounding skin.
Most people (80%) with psoriasis have common plaque psoriasis (also referred to as psoriasis vulgaris – vulgaris just means common) in which the plaques tend to appear most often on the elbows, knees, lower back and scalp, although any part of the body can be affected.
Guttate psoriasis patches are small (often less than 1cm in diameter) and scaly, and can be numerous, covering many areas of the body. It is seen most often in children and teenagers and can be triggered by a throat infection.
The appearance of psoriasis in sensitive areas, such as the armpits and groin is often red and shiny, with little or no scaling.
It is not unusual for psoriasis to be itchy, and it can sometimes feel painful or sore.
Other forms of psoriasis include pustular psoriasis where small blisters appear, usually on the hands and feet and nail psoriasis where changes in the appearance and texture of the nails occur.

What causes it?
Traditionally psoriasis was thought to be a condition of the upper most layer of the skin (the epidermis), but recent research has found that the changes in the skin begin in the immune system when certain immune cells (T cells) are triggered and become overactive. The T cells produce inflammatory chemicals, and act as if they were fighting an infection or healing a wound, which leads to the rapid growth of skin cells causing psoriatic plaques to form. You may therefore hear psoriasis being described as an “auto-immune disease” or “immune-mediated condition”. It is not yet clear what triggers the immune system to act in this way.
Around 30% of people with psoriasis have a family history of the condition, and certain genes have been identified as being linked to psoriasis. However, many genes are involved and even if the right combination of genes has been inherited, psoriasis may not appear. A trigger is required for psoriasis to develop and this could be a throat infection, injury to the skin, certain drugs and physical or emotional stress.

How can psoriasis be treated?
This will depend on the type of psoriasis that you have, and on its severity. Whatever treatment you use it is vitally important to use a moisturiser to make the skin more comfortable. There are four categories of treatments:
1. Topical therapies are treatments that are applied directly to the skin. They are available as creams, lotions, ointments, mousse and gels. Most people with psoriasis will use topical treatments to control the condition. The different categories of topical treatments are: -
· Vitamin D analogues
· Coal tar preparations
· Topical steroids
· Dithranol
· Vitamin A analogues

Should your psoriasis be particularly widespread or not responding to topical treatments you may be referred to a Dermatologist who can prescribe the following treatments:

2. Phototherapy is the term used for treatment with ultraviolet light. There are two types of ultraviolet (UV) light that can be used to treat psoriasis, UVB and UVA. Treatment with UVA requires the use of a chemical agent (either in tablet or bath form) called psoralen. Psoralens make the skin more sensitive to UVA. This treatment is referred to as PUVA therapy. Treatment with UVB does not need psoralens.
You will be required to attend the phototherapy centre 2 or 3 times a week for several weeks if you are receiving UV therapy.

3. Systemic medication refers to treatments you take into your body e.g. tablets. However, they all have potential risks and so are reserved for people with moderate to severe psoriasis. The four main systemic medications used in the UK are:
· Methotrexate - slows down the rate at which the skin cells are dividing in psoriasis
· Ciclosporin - suppresses the immune system
· Acitretin – slows down the rate at which skin cells are dividing in psoriasis, and calms inflammation
· Hydroxycarbamide – also slows down the rate at which the skin cells are dividing in psoriasis.
These treatments will be discussed at length with you should your dermatologist feel you would benefit from taking them. You will require ongoing monitoring with blood tests and blood pressure checks, and some tablets cannot be prescribed if you are taking other medications.

4. Biological injections are new treatments available to treat severe psoriasis that has not responded to any of the aforementioned treatments. They work by blocking the action of certain immune cells (T cells) or the chemicals released by them, which play a part in causing psoriasis.