Derrick Garwood, Freelance Medical Writer and Editor

Here is a nugget of information for the next pub quiz – the term 'psoriasis' comes from the Greek word for 'itch'. Many sufferers have only a few red, scaly patches causing mild discomfort, but virtually the entire skin surface can be affected, as well as the joints, nails and eyes. Dennis Potter, arguably Britain's greatest television playwright, described his condition as follows, "I would have these three month attacks in which I would literally look like a monster – 100% psoriasis – and you also lose control of your temperature, halfway between hallucination and whatever. But also you simply cannot operate, you cannot move, you cannot think".

Approximately 2% of the UK population is affected to some degree by this chronic, non-contagious disorder. The most frequent sites are the front of the knees, back of the elbows and scalp. The typical lesion is a red area, known as a plaque, where the skin is thickened and crusty, often with silvery flakes that are easily detached. This is plaque psoriasis, the most common type, which accounts for approximately 80% of cases. Other forms of the condition include guttate psoriasis (many small red patches all over the body), inverse or flexural psoriasis (red, shiny areas in skin folds), pustular psoriasis (small, circular patches, filled with pus, on the palms of the hands and soles of the feet) and erythrodermic psoriasis (intense redness and swelling of a large part of the skin surface). There are some very clear photographs of these different types on the PsoriasisNet site.

The condition is categorised as mild, moderate or severe, depending upon the percentage of body surface involved and its impact on the patient's quality of life. At a microscopic level, the immune system sends faulty signals that speed up the rate at which skin cells proliferate, move to the surface and are sloughed off. In normal skin this takes about a month: in psoriasis, three to four days. Surface blood vessels dilate to nourish the over-active epidermis and dead skin cells accumulate, forming a white flaky layer. This animation compares the growth cycle in normal skin and a psoriasis lesion.

The clinical perspective at the emedicine site points out that the condition is less common in the tropics and in dark-skinned people, the median age at onset is 28 years, and flares may be related to systemic or environmental events. Significant evidence points to psoriasis being an autoimmune disease, the lesions being associated with increased T-cell activity in the underlying skin, but some authorities regard it as primarily stress-related.

Many studies have indicated that genetic predisposition plays a major role in the pathogenesis of this disorder. The evidence includes a familial tendency to develop the disease, a higher incidence in both identical twins than in both non-identical twins, and a greater frequency of certain white cell antigens in sufferers and their relatives. Last year, three genes on chromosome 17 that are associated with the immune system were identified as being involved in the development of psoriasis, by regulating other genes and the proteins they express. It has also been discovered that variations of the gene responsible for vascular endothelial growth factor (VEGF) occur more frequently in sufferers.

Approximately 10% of psoriasis patients also develop inflammation of the joints, or psoriatic arthritis, generally in the fourth or fifth decades of life. The skin disease and joint disease often appear at different times, sometimes separated by as much as 20 years. Psoriatic arthritis is not as crippling as other forms of arthritis, but if left untreated may lead to discomfort, disability and deformity. The primary feature is distal involvement of the hands, with erosions typically appearing at the peripheral articular surfaces and extending centrally. The five different patterns of arthritis found in the condition are briefly described here and explained in more detail on the John Hopkins University site, which has some very good accompanying photographs.

Psoriasis may also give rise to uveitis, inflammation of the uveal tract of the eye (the iris, ciliary body, or choroid). This is classified anatomically as anterior, intermediate, posterior or diffuse. Symptoms vary considerably depending upon the site and severity, but frequently include 'floaters' and decreased vision. The appearance of the affected eye, particularly in anterior uveitis, can be quite dramatic.

There is no cure for psoriasis and it is difficult to treat. The New Zealand Dermatological Society site provides one of the best accounts of the wide range of available therapies. These are divided into general measures (such as sunshine, baths and rest), topical preparations, ultraviolet treatment and oral medications. Most of the modalities and medications on this overview page have links to more detailed information. If you are particularly interested in topical agents, then it is worth having a look at this page.

Let us conclude the tour by taking a very different tack. As psoriasis is rarely life-threatening but often unsightly, it provides an ideal opportunity for exploitation of vulnerable patients. This site identifies the unscrupulous tactics employed by some marketing operations that use the Internet to advertise miracle cures. There are 'herbal' creams that contain (undisclosed) potent steroids, charging of fees for freely available information, and a product ingredient that causes dermatitis. As for the authoress who rants against conventional medicine, but doesn't even know the difference between contra-indications and adverse events.......!

This tour was submitted by Derrick Garwood, a Freelance Medical Writer and Editor, please feel free to

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