The cause of psoriasis is unknown, but there is a genetic element; many patients have other affected family members. It is not ‘catching’. Approximately 1 in 50 members of the population are affected. There are two main types of psoriasis: ‘chronic plaque psoriasis’ and ‘guttate psoriasis’.
In chronic plaque psoriasis, red scaly raised areas of skin (plaques) develop. The most commonly affected areas are the back of the elbows, front of the knees, scalp and lower back, but any area of skin, including the face, and also the nails, can be affected. It can be itchy, but is not usually very itchy. Approximately 20% of patients with chronic plaque psoriasis develop a form of arthritis called psoriatic arthritis.
Usually psoriasis is diagnosed based on its appearance. If there is doubt, a biopsy can be taken. Chronic plaque psoriasis can go away permanently, but it often persists or reappears intermittently. Unfortunately there is no cure for the condition, but there are treatments that keep it under control. Treatments that are applied to the skin (called ‘topical treatments’) come as creams, ointments, gel, foam and scalp applications. They can contain substances similar to vitamin D, steroids, tar, dithranol, or ‘calcineurin inhibitors’. Moisturising the affected areas (or using a moisturising bath oil) can help, especially to reduce the amount of scale.
Facial psoriasis usually responds well if the correct creams are prescribed. The response of other areas is more variable, and can be difficult to predict. If topical treatments aren’t helpful enough, then light treatment (‘narrowband ultraviolet-B phototherapy’) can be used. If necessary, oral treatments can be used and can be very effective, but they usually have to be taken on an ongoing basis. Over the last decade injection treatments (‘biologics’) have become increasingly used; they are very expensive but very effective.
The second type of psoriasis is called guttate psoriasis. This sometimes occurs two weeks after an episode of tonsillitis. Many tiny red scaly areas appear quickly on the skin. It tends to resolve by itself over a few months, but if necessary this can be speeded up using topical treatments or light treatment.
Other types of psoriasis include ‘flexural psoriasis’, also known as ‘inverse psoriasis’. It affects the armpits, groins, under the breasts, the front of the elbows, behind the knees and the scalp. It can overlap with seborrhoeic eczema, and is then known as ‘sebopsoriasis’. ‘Palmoplantar pustular psoriasis’ affects the palms and soles only; lots of pustules appear at those sites. It almost only ever affects people who smoke.
The psoriasis association is a UK organisation that offers help and support for people affected;
- 1Inflamed patches of skin
- 2Scales on the patches
- 3Cracked skin that bleeds
- 4Sore patches
- 5Burning around the patches
- 6Swollen joints
Dr Roy Palmer, MBBS, MA, MRCP, PhD
Dr Roy Palmer studied pre-clinical medicine at the Oxford University and qualified as a consultant dermatologist in 2002.