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All you need to know about ... psoriasis

Margaret Kelman
Staff Nurse in Dermatology
Queen Margaret Hospital

Psoriasis is a chronic inflammatory skin condition affecting approximately 2% of the Western population, with around 1.2 million sufferers in the UK.1 Typically, psoriasis occurs as a result of the interaction of genetic factors and immune dysfunction, including an increased turnover of skin cells, and environmental factors such as infections, stress and injury to the skin.

In most cases, psoriasis presents as well-demarcated erythematous plaques with a silvery scale on the elbows, knees and scalp, although it can occur on any extensor surface. If the scale is picked this results in bleeding spots due to the extra blood supply to the skin surface and this is referred to as Auspitz Sign.

Psoriasis can also occur at the site of injury or trauma, and this is referred to as the Koebner phenomenon. Changes can also occur in the nails and may include irregular pitting, thickening of the nail and separation of the nail from the nail bed. Around 5% of patients with psoriasis will develop psoriatic arthropathy, which causes stiff and painful joints.1

Variations of psoriasis
Guttate psoriasis presents as widespread small, teardrop-shaped macules (see Figure 1). This form of psoriasis is more common among children and young adults and is commonly triggered by streptococcal infection. Sometimes, treatment with antibiotics will improve symptoms without the need for any other intervention. Other effective treatments involve referral for ultraviolet light therapy and emollients.
Flexural psoriasis affects the skin folds usually in the axillae, perineum, submammory folds, gluteal cleft and groin. Due to friction and humidity in the skin folds there is little or no scale present. Flexural psoriasis will have well-defined, smooth erythematous plaques, which can be confused with seborrhoeic dermatitis.2 Topical treatment usually involves a mild-to-moderate steroid cream with antifungal or antibiotic adjunct as required.

Erythrodermic psoriasis is a severe generalised erythema affecting nearly the whole surface of the skin; characteristically, there is no scale present. This condition can be life threatening, with systemic symptoms such as fever and malaise. Patients are usually treated in hospital.

Palmoplantar psoriasis occurs on the palms and the soles. A variant of this is palmer palnter pustulosis where erythematous papules or plaques develop, with a mixture of yellow and older brown dried up pustules. This condition requires treatment with more potent topical steroid therapy.

Scalp psoriasis causes scale, erythema and itch. Treatment usually involves a coal tar-based shampoo used daily with scalp preparations, eg, coal tar, salicylic acid, vitamin D analogue and topical steroids to remove scale build up, reduce erythema and relieve itch.

Treatments for psoriasis
Emollients are beneficial in the treatment of the dry scaly skin that is characteristic of psoriasis, helping the skin to retain moisture, relieve itch, improve skin function and reduce excessive skin scaling. Although emollients alone will not necessarily clear the psoriasis, they will make the skin more comfortable and help to improve the absorption of more active topical agents.

Topical steroids act rapidly to improve symptoms such as itch and inflammation. Mild topical steroids are suitable for use on the face, flexures and genitalia, and when used for short periods, ie, up to four weeks at a time, do not cause the side-effects associated with long-term use of topical steroids. Potent topical steroids should be used with caution in stable psoriasis as side-effects can occur, including worsening of psoriasis upon stopping. One solution is to use a step down in potency as the skin improves and to use in conjunction with another topical preparation, ie, vitamin D analogue. Very potent topical steroids have been shown to induce generalised pustular psoriasis and should only be used on the palms or soles where the skin is thicker.3

Vitamin D analogues take longer to become effective than topical steroids and it can be six to eight weeks before improvement is noted. But they are easy to use and clean, and can be used safely for long periods as there are no known side-effects if usage is less than 100 g a week for an adult. Some preparations can cause irritation and should be used with caution on face and flexures.

Topical retinoids are vitamin A derivatives and are a useful alternative treatment. They can cause irritation and are best combined with a topical steroid.

Dithranol is suitable for chronic plaque psoriasis where the plaque is localised and clearly demarcated. It needs to be applied accurately to the plaque as it is an irritant to clear skin; therefore, it is a good idea to apply a greasy emollient to the clear skin surrounding the plaque to be treated to prevent irritation.

Coal tar preparations can be used, and the cruder the tar, the more effective the treatment. Visible results can be seen within three to six weeks. The disadvantage is that this form of treatment is messy, which can result in poor compliance. Milder forms of coal tar are available as non-staining preparations but take longer to become effective.3

Sedating antihistamines are effective in treating nocturnal itch and can be a useful adjunct to treatment. They are very much under-prescribed in the management of itch in psoriasis.

At present there isn't a “one cream cures all” and treatment should be considered as a combination therapy taking into account individual preference. It is worth noting that psoriasis can become resistant to treatment after repeated use, so it is a good idea to rotate or combine different treatments to achieve maximum results.3 Expectations of patients, satisfaction with treatment and perception of the condition will all affect their ability to adhere to treatment therapy.

Adherence is the main obstacle in obtaining efficacy of treatments and some 40% of patients declare themselves to be non-compliant.4 So why does this happen? Many patients often lose faith in their skin treatments before they have taken effect. A lot of the topical therapies used for psoriasis can take some weeks before they start to have a visible effect and those that are effective quite quickly, with the exception of topical steroids, tend to be messy and time consuming to apply.

A detailed explanation of how to use the treatments, the duration of therapy expected and how the psoriasis will look and feel as it begins to respond to treatment can increase adherence to topical therapy. Ideally, it should be explained that the psoriasis will not disappear suddenly upon starting treatment but will begin to clear from the centre of the plaque outwards - the centre of the plaque will become flat, leaving a raised edge which is the last to clear. When this area flattens it will leave a slightly darker area on the skin, due to the increased blood supply that occurred when the psoriasis was active and will gradually return to normal over several months.
This is commonly referred to as post-inflammatory hyperpigmentation.5 You can tell if the plaque has cleared by running your finger over the lesion - it should feel smooth to touch with no raised or rough area.

Physiological and social effects of psoriasis
When deciding upon a suitable treatment for psoriasis it is important to take into account not only the visible symptoms of inflammation, thickness of scale and the area of body covered, but also the psychological effect the condition is having on the patient.

Gibbon and Bewley state, “A small plaque of psoriasis on the face or hairline may cause greater psychological damage than more extensive disease hidden by clothing” and many patients feel that “anticipating other people's reactions to their psoriasis affected their ability to socialise”.6 Penzer suggests asking your patient, “Is there one part of your psoriasis that you want to clear more than any other?”, as this can focus their attention onto the more troublesome areas and make treatment seem more achievable.5

Depression is common with psoriasis and the condition can be very distressing for the individual, affecting personal body image, and leading to lack of confidence and low self-esteem. In young adults it was found that 10% had contemplated suicide as a direct result of their psoriasis.6 Various studies have reported that there is a link between depression and itch in psoriasis rather than the severity, visibility or chronic nature of the skin disease.7 Itch as a physical symptom of psoriasis is often very much overlooked. Chronic itch can affect all aspects of quality of life, including difficulty sleeping, problems concentrating, lowered sex drive and depression.

While it is important for patients to understand that there is no cure for psoriasis, there are some very effective treatments to control and relieve symptoms. Patients require advice and support to empower them to manage this chronic condition, including how to access patient support groups. While the majority of people with psoriasis have mild-to-moderate skin disease that is effectively treated in primary care using only topical agents, unfortunately, a minority have severe or resistant skin disease that requires referral to secondary care.

1. Parslew R. How to improve quality of life in patients with psoriasis. Dermatology in Practice 2008;16(1):
2. Khorshid SM. Differential diagnosis of psoriasis. Psoriasis in Practice 2002;1(4):3-4.
3. Pugsley H. Psoriasis management: a primary care perspective. British Journal of Dermatology Nursing  2009;8(3):20-4.
4. Griffiths C. New therapies for psoriasis. British Journal of Dermatology Nursing 2004;8(1):10-11.
5. Penzer R. Providing patients with information on caring for skin. Nursing Standard Supplement 2009;13-19.
6. Gibbon, K. Bewley, A. The psychological effects of psoriasis. Psoriasis in Practice 2002;1(1):6-7.
7. Fortune D, Richards H. Co-morbidity of depression in patients with psoriasis. Dermatology in Practice 2008;16(4):4-7.