Psoriasis is a very common disease, often causing patients embarrassment and distress. It affects about 2 per cent of the population, males and females equally.
Nails and joints may be affected in addition to the skin or in isolation.
Psoriasis can affect people of any age. It can run in families, although it is not thought to be an inherited condition. Trigger factors include beta-haemolytic streptococcus infection, HIV, stress, obesity (a BMI >29 doubles the risk of psoriasis), smoking, alcohol and drugs (e.g. beta-blockers, lithium, antimalarials and withdrawal of steroids).
Psoriasis is a T-cell mediated disease. Epidermal proliferation occurs as a result of activation of the immune system.
There are various types of psoriasis. Plaque psoriasis represents around 90 per cent of cases. The plaques are typically elevated red or pink lesions and are covered by white or silvery scales. The most commonly affected sites are the scalp and extensor surfaces (knees, elbows, lower back).
The plaques are often symmetrical and range in size from a few millimetres to several centimetres.
Other morphological variants are described.
Guttate psoriasis More frequently seen in children and adolescents. It usually occurs following a beta-haemolytic streptococcal or viral infection. Numerous small plaques occur on the trunk. It usually resolves spontaneously.
Erythrodermic psoriasis Total body redness and scaling. This is a dermatological emergency.
Generalised pustular psoriasis This is associated with fever and the patient is systemically unwell. Small, sterile pustules occur. Urgent referral to a dermatologist is needed.
Palmoplantar pustular psoriasis This leads to small pustules on the palms and soles of the feet. It is more common in females. Although potent topical steroids can be tried, many cases are treatment-resistant and will require referral to a dermatologist for systemic treatment.
Occasionally combinations of the different types develop simultaneously or sequentially over time in the same patient.
Nearly half of patients with psoriasis will have some nail changes, usually pitting and onycholysis. This can be difficult to treat.
Up to 30 per cent of patients can be affected by a seronegative arthritis. This affects men and women equally and its incidence peaks between the ages of 30 and 55 years.
In 60 per cent of patients, the psoriasis precedes the arthritis, whereas in 25 per cent of patients the arthritis appears first. In 15 per cent the symptoms occur simultaneously. The severity of arthritis varies between patients.
The different types are as follows:
- Distal interphalangeal involvement
- Asymmetrical oligoarthritis
- Arthritis mutilans.
Treatment of psoriasis
Treatment depends on the extent of the psoriasis, the symptoms present and patient preference. Many patients with small plaques in inconspicuous places choose not to receive treatment.
Lifestyle changes can occasionally be helpful, particularly when stress seems to be a major aggravating factor. Anxiety and depression affects up to 25 per cent of patients with psoriasis and those patients should be treated appropriately.1
Indications for consultant referral
Source: The British Association of Dermatology
Topical treatment is most commonly used. Many of the treatments are messy and time-consuming, meaning compliance can be a problem. For patients with more widespread psoriasis, treatment compliance is improved by specialist nurses, who provide invaluable support and advice.
First-line treatment is a vitamin D3 analogue. This can lead to improvement within two to four weeks in most patients.
However, they are often too irritating to use on the face or the flexures. Combinations with steroids should not be used as maintenance treatment.
Topical steroids are occasionally used, but the psoriasis can worsen after they are stopped. Mild steroids are most frequently used on the face and flexures.
Although coal tar is very effective, it can stain clothing and is very messy. This therefore limits its use. Coal tar bath additives can be useful.
Although dithranol is effective, unfortunately it stains the skin and clothes purple and can also cause severe skin irritation. It should not be used on the face or flexures. In primary care only short-contact self-administered dithranol is used; the cream is applied to lesions for 10-60 minutes and then washed off.
A topical retinoid (e.g. tazarotene) may be effective. This is clean and odourless. Irritation is common but can be minimised by applying tazarotene sparingly to the plaques and avoiding normal skin. It is contraindicated in pregnancy.
Emollients should be used because they can soften scaling and reduce irritation.
Phototherapy can be used with UVB and also UVA combined with either oral or topical psoralen for patients with moderate-to-severe psoriasis.
Systemic treatment should only be considered after both topical treatments and phototherapy have been unsuccessful.
It is usually reserved for patients with very active psoriatic arthritis or who have psoriasis that is physically, psychologically or socially disabling.
Methotrexate is useful in acute, generalised, pustular psoriasis, psoriatic erythroderma, psoriatic arthritis and for extensive moderate-to-severe chronic plaque psoriasis.
Ciclosporin is sometimes used either as a maintenance treatment or as a short course to induce a remission.
Acitretin is an oral retinoid. It is indicated for severe extensive psoriasis resistant to other forms of therapy. It can be used in combination with UVB or PUVA (psoralen plus UVA).
Biological agents have recently been introduced, and have received NICE approval. These target the cytokine TNF-alpha (adalimumab, etanercept and infliximab).
The EMA recently suspended marketing authorisation for efalizumab for psoriasis, and NICE has temporarily withdrawn its guidance on this treatment. Ustekinumab inhibits interleukin 12 and 23, and has recently been licensed in the UK.
These drugs have provided a major advance in treatment but are currently indicated only for limited severe disease owing to lack of data on long-term safety and efficacy.2
Mild psoriatic arthropathy can be treated with NSAIDs and intra-articular corticosteroid injections. Disease-modifying antirheumatic drugs, including azathioprine, methotrexate and ciclosporin are used in severe or progressive disease.
Photochemotherapy may be used to treat peripheral arthritis. Anti-TNF alpha drugs are sometimes used.
- Dr Newson is a GP in the West Midlands
1. Smith C H, Barker J N W N. Psoriasis and its management. BMJ 2006; 333: 380-4.
2. Smith C H, Anstey A V, Barker J N W N, et al. British Association of Dermatologists guidelines for use of biological interventions in psoriasis 2005. Br J Dermatol 2005; 153: 486-97.
- Psoriasis - General Management, British Association of Dermatologists (2008) - http://www.bad.org.uk/site/769/Default.aspx
- Psoriasis Association - www.psoriasis-association.org.uk
- The Psoriasis and Psoriatic Arthritis Alliance - www.papaa.org.