Psoriasis is a skin condition affecting 2-3% of the population of the United Kingdom and Ireland. Im not certain of the Stats for the Rest of the world.
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.
Psoriasis can occur at any point in the lifespan, affecting children, teenagers, adults and older people. It affects males and females equally.
Psoriasis cannot be caught from other people nor can it be transferred from one part of the body to another.
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.
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.
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