PSORIASIS


It presents with rapidly developing widespread redness, followed by the eruption of small pustules on any part of the body. The skin often feels hot to the touch and may be sore, tender or itchy. Systemic illness often occurs. The precise cause of generalised pustular psoriasis is unknown, but potential triggers are thought to include sudden withdrawal of steroids, infection, certain medications or exposure to ultraviolet light.1


NAIL PSORIASIS Nail psoriasis can affect up to 50 per cent of patients with psoriasis. Although commonly seen alongside skin psoriasis, nail psoriasis can occur alone and may go through phases of exacerbation. Signs and symptoms can occur on either fingernails, toenails or both. Nail psoriasis can be easy to misdiagnose as a fungal infection as many of the signs are similar. An affected nail will generally lose its natural shape and feel, with pitting occurring across the surface. Yellow/ orange discolouration, nail thickening and onycholosis (detachment from the nail bed) are also common features. In moderate to severe cases, nail psoriasis can be painful making the use of hands and feet difficult.1,2


GUTTATE PSORIASIS Owing to its small (<1cm) round or oval plaques, guttate psoriasis is also referred to as ‘drop’ psoriasis. Guttate plaques are often bright pink or red on fair skin types. Some fine scaling


may also be present.1 Plaques are


widespread, usually occurring in large numbers across the torso, back and proximal limbs. Lesions can also occur on the face, ears and scalp but it is rarely seen on the soles of the feet.2


Guttate psoriasis can occur at any age, but is more common in children and adults younger than 30 years of age. It is often triggered by a streptococcal throat infection. This form of psoriasis is self-limiting and typically resolves within three to four months of onset. It can occur as a first presentation of psoriasis or as an acute exacerbation of plaque psoriasis. Although long- term prognosis is unknown, it is estimated about a third of people with guttate psoriasis develop chronic plaque disease.1,2


ERYTHRODERMIC PSORIASIS Causing erythromderma (generalised redness of the skin), erythrodermic psoriasis is a rare but dangerous form of psoriasis requiring urgent medical treatment. This form of psoriasis spreads rapidly to typically encompass over 90 per cent of the skin’s surface. Characteristically, the skin is red and hot with the dermatological characteristics of psoriasis often lost. Scale is usually finer and flakier than the classic silvery scale of plaque psoriasis. The patient can quickly become systemically unwell as the condition interferes with thermoregulation. This can result in excessive protein and fluid loss,


leading to dehydration, heart failure and severe illness. Onset can occur acutely over a few days or weeks, or gradually evolve over several months from pre-existing psoriasis.1,2


PSORIATIC ARTHRITIS Between ten and 20 per cent of people with chronic plaque psoriasis will develop psoriatic arthritis. Any joint can be affected but it most commonly affects the joints of the fingers and toes. Any patient presenting with these symptoms should be referred to their GP.1


TREATMENTS


Emollients, in addition to their effects on dryness, itch, scaling and cracking, may have an anti-proliferative effect in psoriasis. Though emollients may be the only treatment necessary for mild psoriasis, they are generally used as an adjunct to other topical treatments; allowing for other active treatments to be better absorbed and therefore work more effectively. Emollients should be used as a soap substitute when bathing or washing and should be applied to the skin before anti- psoriasis treatment and as often as required.5


Keratolytic agents, such as salicylic acid, are useful where there is significant scaling. Topical salicylic acid preparations must not be used by people who are allergic to aspirin and should not be used on inflamed or broken skin.4,5


Coal tar has anti-inflammatory and anti-scaling properties that are useful in chronic plaque psoriasis. A tar- based shampoo is an effective OTC treatment for scalp psoriasis. SIGN recommend initial treatment with overnight application of salicylic acid, tar preparations, or oil preparations (eg, olive or coconut oil) for those patients with thick scaling of the scalp.5


Dithranol prevents T-lymphocyte activation and normalises skin cell differentiation. Contact with normal skin must be avoided as it causes irritation and staining of skin and clothing. Therapy should be short contact (around 30 minutes). Dithranol should be discontinued if it causes acute inflammation - continued use can result in the psoriasis becoming unstable. Patients should use gloves and wash hands thoroughly after using these preparations.4,5


Vitamin D analogues, including calcipotriol, act by encouraging normal


48 - SCOTTISH PHARMACIST


skin cell growth due to their effects on cell division and differentiation.5 SIGN recommend vitamin D analogues as first line for the long-term topical treatment of chronic plaque psoriasis.4


Topical corticosteroids are one of the first treatment options for those whose psoriasis covers <5% of their body or is currently in exacerbation. However, long-term use can lead to skin atrophy and can cause psoriasis to become unstable.5


SIGN recommend short-term intermittent use of a potent topical corticosteroid (eg, betamethasone) or a combined potent topical corticosteroid plus calcipotriol ointment to gain rapid improvement in plaque psoriasis. Short-term intermittent use of a potent topical corticosteroid or a combined potent corticosteroid and a vitamin D analogue is recommended in scalp psoriasis. Moderate potency topical corticosteroids (eg, clobetasone) are recommended for short-term use in facial and flexural psoriasis.4


If other topical therapies have failed, Tacrolimus can be considered as it reduces inflammation through its action as a calcineurin inhibitor. Alternatively, the retinoid Tazarotene can be used to treat well-defined plaques if other therapies have been ineffective.4,5


For severe, resistant, unstable or complicated forms of psoriasis, ultraviolet light therapy and systemic treatments including methotrexate, ciclosporin and acitretin can be initiated under specialist supervision in secondary care.5


• REFERENCES


1. Psoriasis Association UK. https:// www.psoriasis-association.org.uk/ psoriasis-and-treatments/ [Online]


2. Patient UK. Psoriasis. https:// patient.info/health/psoriasis-leaflet [Online]


3. British Association of Dermatologists. Psoriasis – An Overview. http://www. bad.org.uk/shared/get-file. ashx?id=178&itemtype=document [Online]


4. SIGN Guideline 121. http://sign. ac.uk/guidelines/fulltext/121/index. html [Online]


5. British National Formulary Issue 73.


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