What is psoriasis?
Psoriasis is a common inflammatory skin disease affecting 2% of the population. It occurs equally in men and women, can appear at any age, and tends to come and go unpredictably. It is not infectious, therefore you cannot catch psoriasis from someone else. It does not scar the skin although sometimes it can cause a temporary increase or reduction in skin pigmentation. Although psoriasis is a long-term condition there are many effective treatments available to keep it under good control. Psoriasis can affect the nails and the joints as well as the skin. About half of people with psoriasis have psoriasis affecting the nails.
For people with moderate to severe psoriasis about one in three will develop psoriatic arthritis at some time. Psoriatic arthritis produces swelling and stiffness in the joints or stiffness in the lower back and should be managed by a rheumatologist who works closely with your dermatologist and/or your GP.
Psoriasis, particularly moderate to severe psoriasis, is associated with an increased risk of anxiety and depression. Moderate to severe psoriasis increases the risk of heart disease and stroke and treatment of psoriasis may reduce this risk. Psoriasis can also be associated with an increased risk of harmful use of alcohol and with diabetes and obesity.
What causes psoriasis?
Both inherited and environmental factors play a role in the development of psoriasis. Some people are more likely to develop psoriasis than others, particularly if someone in their family has psoriasis. Skin affected by psoriasis is red and scaly. The outer layer of skin (the epidermis) contains skin cells which are continuously being replaced. This process normally takes between three and four weeks. In psoriasis, the rate of turnover is dramatically increased so that cells are formed and shed in as little as three or four days. For many individuals factors such infections, stress, alcohol and/or smoking have a role triggering flares of psoriasis. Certain medications such as beta blockers (used to treat high blood pressure and angina), lithium and tablets used to treat malaria, can also cause psoriasis to flare. The relationship between diet and psoriasis has not been fully established, but obesity is associated with psoriasis and exercise and losing weight can be beneficial.
Is psoriasis hereditary?
Yes, but the way it is inherited is complex.
What are the symptoms of psoriasis?
· Psoriasis may not have any associated symptoms but it can be itchy and painful. Certain sites such as the scalp, lower legs and groin can be particularly itchy. If psoriasis affects the hands and feet, painful fissures or cracks can develop and these can affect use of the hands and walking. Severe psoriasis on the body can also develop fissures which are painful and can bleed.
· Psoriasis can affect the nails and lifting of the nail plate from the nail bed can be painful.
· Psoriatic arthritis produces pain, swelling and stiffness in one or more joints, particularly in the morning.
What does psoriasis look like?
The skin changes of psoriasis (often known as plaques) are pink or red areas with silvery-white scales. Many people have just a few plaques but individuals with moderate to severe psoriasis may have several plaques covering large areas of their body.
Four patterns of psoriasis are recognised:
· Chronic plaque psoriasis is the most common type of psoriasis. Plaques of psoriasis are usually present on the knees, elbows, trunk and scalp, although others areas can be involved too.
· Guttate psoriasis consists of small plaques of psoriasis scattered over the trunk and limbs. It can be precipitated by a bacteria called Streptococcus which can cause throat infections.
· Palmoplantar psoriasis is psoriasis affecting the hands and feet. Psoriasis may appear at other sites too.
· Pustular psoriasis is rare type of psoriasis where the plaques on the trunk and limbs are studded with tiny pus spots. It can be localised or generalised and can flare rapidly necessitating hospital admission for treatment. Nail psoriasis is present in about half of people with psoriasis. The features of nail psoriasis are:
· Pitting (indentations) of the surface of the nail;
· Salmon pink areas of discolouration under the nail;
· Separation of the nail plate from the nail bed; and
· Thickening of the nails.
How will psoriasis be diagnosed?
· Psoriasis is usually diagnosed on the appearance and distribution of the plaques.
· Psoriatic arthritis is usually diagnosed by a rheumatologist but your dermatologist or GP may ask you if you have any joint symptoms or ask you to complete a screening questionnaire.
How is psoriasis assessed?
Psoriasis may be assessed using a variety of tools:
· Physician global assessment (PGA): this ranges from mild to very severe and is a physician’s overall impression of the severity of the psoriasis.
● Patient global assessment: this is the same as the physician global assessment but is the overall impression of the severity of psoriasis provided by the person with psoriasis.
· PASI (Psoriasis Area and Severity Index) is calculated by looking at four areas: the head and neck, upper limbs, lower limbs and the trunk. In each of these areas the redness, scaliness, thickness and surface area affected are assessed and used to calculate the PASI score. This score ranges from 0–72 with 0 being no psoriasis and 72 being severe. In practice any score above 10 indicates severe psoriasis.
· DLQI (Dermatology Life Quality Index) is a series of 10 questions which asks how psoriasis has impacted on your life in the past 7 days. The score ranges from 0–30 with 0 indicating no impact and a score above 10 indicating a considerable impact on quality of life. DLQI does not assess distress.
· PEST score (Psoriasis Epidemiology Screening Tool) is used to screen for possible psoriatic arthritis.
· HADS (Hospital Anxiety and Depression Scale) or other scales may be used to screen for depression and/or anxiety.
Blood tests may be recommended by your GP or dermatologist. If you are considering tablet treatment for your psoriasis then blood tests will be needed before and during treatment.
Can psoriasis be cured?
There is no cure for psoriasis but there are several effective treatments available. For information about treatments please visit this page on the website of the British Association Dermatologists.