Psoriasis is a long-term skin condition that can also affect the nails and joints. It tends to flare up from time to time. Treatment with various creams or ointments can often clear or reduce patches (plaques) of psoriasis. Special light therapy and/or powerful medication are treatment options for severe cases where creams and ointments have not worked very well. People with psoriasis are more likely than usual to develop cardiovascular disease (heart disease and strokes).
What is psoriasis?
Psoriasis is a common condition where there is inflammation of the skin. It 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 psoriasis clears for long spells. However, in some people the flare-ups occur often. Psoriasis is not due to an infection. You cannot pass it on to other people and it does not turn into cancer.
What are the different types of psoriasis?
There are different types of psoriasis. However, chronic plaque psoriasis (described below) is by far the most common and typical type.
The Primary Care Dermatology Society has published a ‘Treatment pathway’ – see Further Reading below. This has several pictures that may be useful, as well as a clear plan for treatment of the different areas and types of psoriasis. This includes often difficult to treat areas such as the face, the hands and the genital area.
Chronic plaque psoriasis
Between 8 and 9 out of 10 people with psoriasis have chronic plaque psoriasis. The rash is made up of patches (plaques) on the skin. The picture shows typical plaques of psoriasis next to some normal skin.
Each plaque usually looks pink or red with overlying flaky, silvery-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 and the lower back. However, it may appear anywhere on the skin, including:
This affects roughly half of people with chronic plaque psoriasis of the skin of their body. However, scalp psoriasis may occur alone in some people. It looks like severe dandruff. The whole scalp may be affected, or there may just be a few patches. If severe, it can lead to hair loss in some people.
This is also a type of chronic plaque psoriasis but the affected skin looks slightly different – it is red and inflamed but the skin is smooth and does not have the rough scaling. It occurs in the creases of the skin (flexures) such as in the armpit, in the groin, under breasts and in skin folds.
The extent of the psoriasis varies between different people and can also vary from time to time in the same person. Many people have just a few small plaques of a centimetre or so when their psoriasis flares up. Others have a more widespread rash with large plaques of several centimetres across. Chronic plaque psoriasis can be itchy but it does not usually cause too much discomfort.
This is the second most common type of psoriasis. It usually just affects the palms of the hands and soles of the feet. (It is sometimes called palmoplantar pustulosis.) Affected skin develops crops of pustules, which are small fluid-filled spots. The pustules 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 is a more serious form of psoriasis and needs urgent treatment under the care of a skin specialist (a dermatologist).
About half of people with any type of psoriasis also get fingernail psoriasis. In some people toenails are also affected. Nail psoriasis may also occur alone without any skin rash. See the separate leaflet called Psoriatic Nail Disease for more details.
Guttate (drop) Psoriasis
This is a type of psoriasis where the trigger is known to be a germ (bacterium). It typically occurs following a sore throat. See the separate leaflet called Guttate Psoriasis for more details.
This type of psoriasis is rare. It causes a widespread redness (erythema) of much of the skin surface, which is painful. Individual plaques of psoriasis cannot be seen because they have merged together. There is still redness and scaling of the skin and the skin feels warm to touch. A person with erythrodermic psoriasis may also have a high temperature (fever). It is serious and needs urgent treatment and admission to hospital because it can interfere with your body’s ability to control your temperature and also causes lack of fluid in the body (dehydration).
What Causes Psoriasis?
Normal skin is made up of layers of skin cells. The top layer of cells (horny layer of the epidermis) is flattened and gradually sheds (they fall off). New cells are constantly being made underneath (in the basal layer of the epidermis) to replace the shed top layer. Cells gradually move from the basal layer to the top horny layer. It normally takes about 28 days for a cell in the basal layer to reach the top layer of skin and to be shed. The diagram above shows a cross-section of normal skin.
People with psoriasis make more skin cells than normal and make them more quickly. The skin also becomes inflamed. The cause of these changes isn’t fully understood but it is now thought that psoriasis is probably an autoimmune disease. Normally the immune system destroys anything that is foreign – eg, bacteria or viruses. In autoimmune diseases, the immune system mistakenly treats parts of the body as foreign. Inherited (genetic) factors also seem to play a part. It may be that some factor in the environment (perhaps a virus) triggers the condition to start in someone who is already genetically prone to develop it. Research continues to try to find the exact cause.
Treatment of Psoriasis
Patients with psoriasis should ensure they are well informed about their skin condition and its treatment. There are benefits from not smoking, avoiding excessive alcohol, and maintaining optimal weight.
Mild psoriasis is generally treated with topical agents alone. Which treatment is selected may depend on body site, extent and severity of psoriasis.
- Coal tar preparations
- Salicylic acid
- Vitamin D analogue (calcipotriol)
- Topical corticosteroids
- Combination calcipotriol/betamethasone dipropionate ointment/gel or foam
- A calcineurin inhibitor (tacrolimus, pimecrolimus)
Most psoriasis centres offer phototherapy with ultraviolet (UV) radiation, often in combination with topical or systemic agents. Types of phototherapy include:
- Broadband UVB
- Photochemotherapy (PUVA)
- Targeted phototherapy
Many other monoclonal antibodies are under investigation in the treatment of psoriasis.
Even though psoriasis is a benign skin disorder, it is a lifelong illness with no cure. Everyone undergoes remissions and relapses and overall it leads to poor quality of life. Today there are several reports indicating that psoriasis also increases the risk of adverse cardiac events. Psoriasis also is associated with alcoholism, smoking, depression, risk of lymphoma, suicide, adverse drug reactions and several types of skin cancers. Evidence continues to mount that psoriasis is associated with hypertension, renal disease, and heart disease. Overall, patients with psoriasis involving the palms and soles tend to have a much poorer quality of life than those who have psoriasis on other parts of the body.