Questions from practice — Pityriasis versicolour
This skin condition is probably pityriasis versicolor (PV; previously called tinea versicolor). Typically this appears as small pink or light brown patches on untanned skin or pale patches on tanned skin. Such changes most commonly appear on the trunk and upper limbs and young adults are most commonly affected.
“Pityriasis” means bran-like scale and sometimes fine scaling can be seen on the patches. The condition can be mildly itchy but usually it causes no problems other than concern over its appearance — affected areas of skin will fail to tan.
PV is caused by proliferation of the yeast, Malassezia furfur (previously called Pityrosporum orbiculare), which is part of the normal flora of human skin. The infection is confined to the uppermost layer of the epidermis, the stratum corneum. PV is not considered to be a contagious disease because the causative organism is part of the normal flora.
It is not known why some people develop PV and others do not but the main predisposing factor is a warm, humid environment. Other factors include immunosuppression and Cushing’s disease.
PV can be treated with topical antifungals. Although antifungal shampoos are primarily designed to treat scalp conditions, they can be effective for PV. The product this customer used before was probably ketoconazole 2 per cent shampoo, which may be prescribed for PV.
The shampoo should be applied to wet skin and left on for three to five minutes before washing off. It should be used daily for five days. However, the licences for the over-the-counter products limit their use to the treatment of scalp conditions.
Selenium sulphide 2.5 per cent shampoo can also be used to treat PV and is often recommended by dermatologists (unlicensed indication). It should be diluted with an equal quantity of water and painted on to the affected area. It should be left for 30 minutes or overnight before washing off.
Recommendations about the frequency of application vary from two to seven times over two weeks. Some patients find the treatment causes irritation.
Topical imidazole antifungal creams, such as clotrimazole, miconazole, econazole and ketoconazole, can all be used to treat PV. Creams should be applied daily for two weeks. Clotrimazole spray would be an effective way to treat large or hairy areas. It should be noted, however, that although they are the same, the P product (Canesten Dermatological Spray) is licensed for PV but the GSL (Canesten AF) product is not.
Oral treatment with azole antifungals (eg, itraconazole 200 mg daily for seven days) is usually only reserved for people whose condition has failed to respond to topical treatment.
It is difficult to know if a treatment has worked in the short term because it may take several weeks or months for the colour changes to be reversed. Fortunately PV does not cause scarring or permanent skin colour changes. However, recurrence is common and prophylaxis with weekly use of any of the topical agents is recommended for susceptible individuals, particularly before a holiday in a hot, humid place.
People should be referred to their GPs if the diagnosis is in doubt (eg, extensive PV can be confused with vitiligo) or if they have failed to respond to topical treatments and might need oral antifungals.
Pityriasis versicolor should not be confused with pityriasis rosea, which is thought to be caused by a reaction to a virus. This condition presents with a pink, itchy, scaly rash, usually preceded by one large pink, itchy patch (called a herald patch). The condition resolves spontaneously over a couple of months. Mild topical corticosteroids and antihistamines are used for symptomatic treatment.
Christine Clark is a freelance pharmaceutical writer, Lancashire
Citation: The Pharmaceutical Journal URI: 11002409
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