What is Psoriasis?

This Skin Disorder is Characterised by Red Skin and Scaly Patches

Feb 2, 2009 John Richard Roberts

Psoriasis is unpleasant and can be embarrassing. Although the cause is unknown, its nature is thought to be autoimmune and triggered by various factors.

It is a skin disorder that many will be familiar with if not in themselves then in a friend or family member. Psoriasis affects around two in a hundred people and can appear at any age – males and females are equally affected.

The condition is not normally life threatening but it can be uncomfortable and, like many skin diseases, embarrassing.

Clinical Features of Psoriasis

The most common presentation is of red patches of skin topped with gray scales. These are usually found at the front of the knees, back of the elbows and on the scalp. However, the lesions can appear almost anywhere on the body. The patches may be very itchy or produce no physical discomfort at all. In some cases the nails are involved leading to pitting and thickening

Variations occur: one in which the patches are very red with greatly increased blood flow and the other comprised of small pustules. Rarely, these two variants may produce severe illness.

Psoriasis is generally a chronic condition sometimes lasting very many years although the severity tends to vary.

Psoriatic Arthritis

In around 5% of sufferers psoriasis is associated with a type of arthritis producing swelling and pain in the joints and sometimes back pain. The condition is known to be genetically linked.

Cause of Psoriasis

Psoriasis is an inflammatory dermatosis meaning that the dermis becomes inflamed. Among other things this leads to increased cell production in the skin causing the thickened and scaly appearance of the epidermis (the outer skin). The reason is unclear but the mechanism is probably autoimmune and susceptibility is genetically linked.

Prone individuals may develop the illness through one of a number triggers including trauma, infection, stress and some types of medication.

Treatment of Psoriasis

• Emollients: these hydrate and soothe the skin. Common examples are aqueous cream and soft paraffin ointment. They are suitable for mild cases or as an adjunct to other therapy in more severe examples of the disease.
• Vitamin D analogues: these chemicals, related, to vitamin D, are useful because they affect cell production. Examples are: calcipotriol and tacalcitol.
• Coal tar: although smelly and messy it is normally well-tolerated by the skin and has anti-inflammatory and anti-scaling effects.
• Salicylic acid: related to aspirin, helps remove the scaly skin. Usually combined with an emollient or coal tar.
• Dithranol: otherwise known as anthralin. Sometimes mixed with coal tar and salicylic acid.
• Steroid creams: used for many inflammatory conditions. Generally used only for small patches of psoriasis as there is a risk of increasing the severity of the condition.
• Phototherapy: use of ultra-violet light and available in specialist centres. Sometimes used in conjunction with a cream or drug which enhances the therapeutic effect.
• Systemic treatment: use of medication taken by mouth or injection. Used only in severe cases. Most of these drugs depress the immune system and inflammatory mechanisms. Acitretin – a derivative or vitamin A is used under specialist supervision.
• Diet: various diets have been suggested as a treatment for psoriasis such as fish oils and avoiding dairy products. As yet there is no firm evidence to support these.

This article is for information only. If you have any health concerns you should consult your doctor.

Resources

British National Formulary BMA 2006

Medicine Moxham and Souhami. Churchill Livingstone 2002

The Cochrane Collaboration.

The copyright of the article What is Psoriasis? in General Medicine is owned by John Richard Roberts. Permission to republish What is Psoriasis? in print or online must be granted by the author in writing.

Skin Cross Section