What is psoriasis?
Being told you have the skin condition psoriasis can be devastating. We all tend to have an image of psoriasis based on very severe cases such as the playwright Dennis Potter. But, although it inevitably takes some time to adjust to the diagnosis, you can take some comfort from knowing that psoriasis usually comes and goes, occasionally disappears forever, and varies from very mild to the much rarer, more severe forms.
Psoriasis is surprisingly common, affecting one to three per cent of most populations in the world. It tends to be particularly common in Europe and the USA and least common in black West Africans and Latin Americans. Psoriasis affects men and women equally. It can start at any age, but often occurs for the first time in five- to nine-year-old girls and in 15- to 19-year-old boys. It can also start for the first time in men and women between the ages of 57 and 60 years.
No one knows for certain what causes psoriasis. You can inherit the tendency to have the condition, so psoriasis may run in your family. This tendency can then be activated by an infection, certain drugs or stress, although it is often impossible to identify specific triggers. There are also some abnormalities of chemicals in skin cells that interact and contribute to the characteristic skin changes seen in psoriasis. One thing is for certain, there is no virus or bacterium involved in the skin. You cannot catch psoriasis from others, and you cannot infect others with psoriasis if you have the condition yourself.
Psoriasis causes pink or red, raised patches of skin. These patches look very distinct from the rest of the normal-looking skin because they have a well-defined edge around them. They are called ‘plaques’ by doctors. The plaques have a scaly surface and may range in size from tiny to very large. Some people with psoriasis also experience itching.
The plaques are caused by abnormal skin cell replacement. Your skin constantly replaces its outermost layer (the epidermis) because the cells get rubbed off while you go about your daily life. In people with psoriasis, the epidermal cells are replaced too quickly and over-enthusiastically. The cells that come to the surface are not properly formed and get heaped up into the plaques. Underlying blood vessels are also damaged, causing the redness that often occurs in psoriasis. White blood cells, which move into the the plaques, can form pustules in the epidermis. These blisters or pustules may appear on the soles of the feet and palms of the hands.
Changes can also occur in the nails, which may become thickened and damaged, and contain tiny pits. A minority of people with psoriasis also develop joint problems – for more on this, see ‘Psoriasis and other diseases + lifestyle issues’ on page 51.
It is very hard to predict whether your psoriasis will worsen, improve or stay the same throughout your life. Psoriasis tends to remain a long-standing (chronic) problem, although there are usually some periods when it is much better and others when it flares up.
There is no overall cure for psoriasis, although it does sometimes just disappear of its own accord. However, the treatments have greatly improved in recent years, and although coping with psoriasis is still a great challenge for many, the help available is better now than it has ever been before.
In psoriasis, the skin renews itself in four days instead of 28 days
The silvery, scaly patches of skin are called plaques
Plaques consist of immature skin cells
Immunological factors play a role in the formation of plaques