Pustular psoriasis

In this rare form of psoriasis sterile pustules are an obvious clinical feature. The pustules tend to be located on the advancing edge of the lesions and typically occur on the palms of the hands and soles of the feet (Fig. 7.5).

Seborrhoeic psoriasis (also known as flexural psoriasis)

Seborrhoeic psoriasis refers to classic lesions that affect the scalp but with less typical lesions (lack scaling) in the body folds, especially the groins and axillae. Often, in mild cases the scalp might be the only part of the body involved. Itch, in this form, can be prominent.

Guttate psoriasis (also known as raindrop psoriasis)

Guttate psoriasis is characterised by crops of scattered small lesions (less than 1 cm) covered with light flaky scales that often affects the trunk and proximal part of the limbs (Fig. 7.6). This form of psoriasis usually occurs in adolescents and often follows a streptococcal throat infection and in people genetically predisposed to psoriasis. The condition is usually self-limiting.

Erythrodermic psoriasis

Erythrodermic psoriasis presents as an extensive erythema and shows very few classical lesions. It is therefore difficult to diagnosis. The condition is serious and can even be life threatening. Systemic symptoms can be severe and include fever, joint pain and diarrhoea. Patients are extremely unlikely to present at a community pharmacy.

Tinea corporis

Tinea corporis can superficially look like plaque psoriasis. For further information on tinea infection see page 210.

Lichen planus

Lichen planus is an uncommon condition and is reported to only account for 0.2 to 0.8% of dermatological outpatient consultations. The lesions are similar in appearance to plaque psoriasis but are itchy and are normally located on the inner surfaces of the wrists and on the shins, an atypical distribution for psoriasis. Additionally, oral mucous membranes are normally affected with white, slightly raised lesions that look a little like a spider’s web. The person will not have a family history of psoriasis.

Pityriasis rosea

The condition is characterised by erythematous scaling mainly on the trunk, but also on the thighs and upper arms. The colour of the rash tends to be a lighter pink colour than psoriasis and can be mildly itchy. A ‘target’ disc lesion, often misdiagnosed as ringworm, is followed 1 week later with an extensive rash. It most commonly affects young adults. The condition usually remits spontaneously after 4 to 8 weeks. An accurate history will normally eliminate pityriasis rosea from psoriasis, as the condition is acute in onset and the patient can often identify the initial ‘target’ lesion.

Medication-exacerbated psoriasis

A number of medicines can worsen or aggravate existing psoriasis. Medication most commonly associated are lithium, antimalarials and beta-blockers. Other less commonly implicated include digoxin, amiodarone, clonidine, penicillin, tetracycline, terbinafine, bupropion and sulphonamides. In addition systemic corticosteroids have been shown to induce flares in psoriasis patients.

Seborrhoeic dermatitis

Mild scalp psoriasis can be very difficult to distinguish from seborrhoeic dermatitis. However, in practice this is rarely a problem since treatment for both conditions is often the same. For further information on seborrhoeic dermatitis see page 207.

Tinea capitis (fungal infection of the scalp)

Tinea capitis is an uncommon infection but if the patient has scaling skin, broken hairs and a patch of alopecia then a tinea infection should be considered.

Figure 7.7 will aid in the differentiation of plaque psoriasis.

Emollients

No published literature appears to have addressed either emollient efficacy or whether one emollient is superior to another in treating psoriasis. Subjective evidence over a long period of time has shown that emollients are useful and are an important aspect of psoriasis treatment. Emollients are frequently prescribed and used to help soften scaling and soothe the skin so reducing irritation, cracking and dryness. On current evidence there is no way of knowing if one emollient is superior to another. Patients might have to try several emollients before finding one that is most effective for their skin.

Keratolytics

Keratolytics, such as salicylic acid and lactic acid have been incorporated into emollients to aid clearing scale and are often used for scalp psoriasis where very thick scaling can occur. Although there appears to be no published evidence for their efficacy in clearing scale, clinical practice suggests that they should be used first when significant scaling is present before using other treatments.

Coal tar

Goeckerman demonstrated the effectiveness of coal tar as early as 1925. This remained the mainstay of treatment until the introduction of dithranol, corticosteroids, and more recently, vitamin D and A analogues. A number of clinical studies have confirmed the beneficial effect coal tar has on psoriasis, although a major drawback in assessing the effectiveness of coal tar preparations is the variability in their composition making meaningful comparisons between studies difficult. Comparisons between coal tar and other treatment regimens have been conducted. Tham et al (1994) compared the effectiveness of calcipotriol 50 µg twice daily versus 15% coal tar solution each day. Both treatments were shown to be effective, although calcipotriol was significantly better than the coal tar solution. Harrington (1989) compared two pharmacy-only products, Psorin and Alphosyl. Findings showed that both helped in the treatment of psoriasis but Psorin (which includes 0.11% dithranol) was significantly more effective.

Dithranol

Dithranol was first used in the 1950s and has become an established treatment option as clinical trials have established its efficacy. A systematic review in 2009 identified three placebo-controlled trials with dithranol, all demonstrating a statistically significant improvement over placebo (Mason et al 2009). There appears to be no definitive answer as to which strength is most appropriate, however, current practice dictates starting on the lowest possible concentration and gradually increasing the concentration until improvement is noticed. In addition, short contact regimens are advocated. However, one review of published studies involving short-contact dithranol therapy concluded that due to methodological flaws in many of the trials it is impossible to objectively determine the efficacy of this regimen (Naldi et al 1992).

Emollients

All emollients should be regularly and liberally applied with no upper limit on how often they can be used. All are chemically inert and can therefore be safely used from birth onwards by all patients. They do not have any interactions with other medicines. For more information on emollients see page 242.

Tar-based products

All patient groups, including pregnant and breastfeeding women, can use the majority of products on either the skin or scalp. They have no drug interactions but can cause local skin or scalp irritation and stain skin and clothes. There has been recent concern over topical tar products association with an increased risk of skin cancer, although there is at present no firm epidemiological evidence (http://www.bad.org.uk/site/1114/default.aspx; accessed 13 November 2012).

Dithranol (e.g. Dithrocream)

Dithranol preparations are pharmacy-only medicines so long as the strength does not exceed a maximum of 1.0%. Although dithranol has evidence of efficacy, recommendation is not advocated in a pharmacy context due to its adverse effects, even at low concentrations. When used, short-contact therapy is often advocated because prolonged exposure can lead to irritation and burning skin. This involves using the lowest strength for the shortest period, which controls symptoms.

Seborrhoeic dermatitis

Typically, seborrhoeic dermatitis will affect areas other than the scalp. In adults, the trunk is commonly involved, as are the eyebrows, eyelashes and external ear. If only scalp involvement is present then the patient might complain of severe and persistent dandruff and the skin of the scalp will be red. For further information on seborrhoeic dermatitis see page 207.

Contact dermatitis

Enquiry should be made to the use of new hair products such as dyes and perms. These can cause irritation and scaling. Avoidance of the irritant should see an improvement in the condition. If improvement is not observed after avoidance of 1 to 2 weeks then a re-assessment of the condition is needed.

Tinea capitis

If the problem is persistent and associated with hair loss then fungal infection of the scalp should be considered.

Figure 7.8 will aid the differentiation of dandruff from other scalp disorders.

Coal tar

The mechanism of action for crude coal tar in the management of dandruff is unclear, although it appears that tars affect DNA synthesis and have an antimitotic effect. There are virtually no published studies in the literature to assess the efficacy of coal tars in the treatment of dandruff. A review in Clinical Evidence identified one study comparing coal tar to placebo (Manrìquez & Uribe 2007). The study involving 111 people with seborrhoeic dermatitis or dandruff found coal tar reduced dandruff scores and redness compared to placebo at 29 days. Despite the lack of evidence, tar derivatives are found in a plethora of OTC medicated shampoos and have been granted FDA approval in America as an antidandruff agent.

Selenium sulphide

Selenium is thought to work by its antifungal action. It is accepted that selenium is effective as an antidandruff agent and studies have shown it to be significantly better than placebo and non-medicated shampoos.

Zinc pyrithione

Zinc pyrithione, like selenium, exhibits antifungal properties but also reduces cell turnover rates. It is believed that one or both of these properties confers its effectiveness in treating dandruff. Few trials have been conducted with zinc pyrithione although trials have shown significant improvement in dandruff severity scores.

Ketoconazole

Ketoconazole, an azole antifungal, inhibits M. ovale replication by interfering with cell membrane formation. It helps in controlling the itching and flaking associated with dandruff. Studies have shown it to be an effective treatment. It has been demonstrated that ketoconazole is significantly better than zinc pyrithione and has similar efficacy to selenium, although it is better tolerated than selenium. Ketoconazole has also been shown to act as a prophylactic agent in preventing relapse.

In addition to the ingredients listed, salicylic acid is an ingredient in some combined products (e.g. Capasal and Meted) and included for its keratolytic properties, although trials are lacking to substantiate its effect.

Coal tar products

Products containing coal tar are discussed under practical prescribing for psoriasis. For further information on coal tar products see page 203.

Selenium sulphide (e.g. Selsun)

Adults and children over the age of 5 should use the product twice a week for the first 2 weeks and then once a week for the next 2 weeks. The hair should be thoroughly wet before applying the shampoo and left in contact with the scalp for 2 to 3 minutes before rinsing out. Selenium should be avoided if the patient has inflamed or broken skin because irritation can occur. Selenium can also cause discolouration of the hair and alter the colour of hair dyes.

Zinc pyrithione (e.g. Head and Shoulders)

Zinc-based products can be used by all patients and at any age. It should be used on a daily basis until dandruff clears. Dermatitis has been reported with zinc pyrithione and should be borne in mind when treating patients with pre-existing dermatitis.

Ketoconazole (Nizoral Dandruff and Nizoral Anti-Dandruff Shampoo)

Nizoral can either be used to treat acute flare-ups of dandruff or as prophylaxis. To treat acute cases adults and children should wash the hair thoroughly, leaving the shampoo on for 3 to 5 minutes before rinsing it off. This should be repeated every 3 or 4 days (twice a week) for between 2 and 4 weeks. If used for prophylaxis, the shampoo should be used once every 1 to 2 weeks. It can cause local itching or a burning sensation on application and may rarely discolour hair.

Atopic dermatitis

In infants, atopic dermatitis usually presents as itchy lesions on the face and trunk. Scalp involvement is less common and the nappy area is usually spared. A positive family history of the atopic triad of dermatitis, asthma or hay fever is common. For further information on differentiating atopic dermatitis see page 291.

Psoriasis

Adults with scalp psoriasis can be confused with those patients who present with severe and persistent dandruff caused by seborrhoeic dermatitis. However, in scalp psoriasis the plaques tend to be crusty and extend away from the hairline where as seborrhoeic dermatitis causes scaling with underlying redness. It also affects the eyebrows and eyelids, unlike psoriasis.

Pityriasis versicolor (meaning bran-like scaly rash of various colour)

Pityriasis versicolor, a yeast infection, can be mistaken for adult seborrhoeic dermatitis because the lesions exhibit fine superficial scale and are located on the upper trunk. The lesions are usually small (less than 1 cm) but can join together to form larger plaques. The condition is associated with warm climates and most people will have picked the infection up when on holiday. The rash does not itch significantly and the face is usually spared. It can be treated with antifungal lotions and shampoos (see Dandruff page 206), or if a small number of lesions with imidazole creams (see Fungal infections page 213). Antifungal shampoos such as ketoconazole, and selenium sulphide (2.5%) are applied for 10 minutes and then washed off, and this is repeated daily for 10 days. Imidazole creams are applied daily for 10 days.

Rosacea

Rosacea predominately affects the face – an area usually involved in adult seborrhoeic dermatitis. For more information on rosacea see page 233 under the acne section.

Dentinox Cradle Cap Shampoo

This contains sodium lauryl ether sulphosuccinate 6% and sodium lauryl ether sulphate 2.7%. The shampoo should be applied twice during each bath time until the scalp clears, after which it can be used when needed.

Athlete’s foot

Athlete’s foot is characterised by itching, flaking and fissuring of the skin and will appear white and ‘soggy’ due to maceration of the skin (Fig. 7.13). The feet often smell. The usual site of infection is in the toe webs, especially the fourth web space (web space next to the little toe).

Once acquired the infection can spread to other sites including the sole and instep of the foot. Over time this can infect the nails (see page 216 for fungal nail infection). Cases of tinea infection where the plantar surface has become involved may be persistent and difficult to treat.

Tinea corporis

Tinea corporis is defined as an infection of the major skin surfaces that do not involve the face, hands, feet, groin or scalp. The usual clinical presentation is of itchy pink or red scaly slightly raised patches with a well-defined inflamed border (Fig. 7.14). Over time the lesions often show ‘central clearing’ as the central area is relatively resistant to colonisation. This appearance led to the term ringworm. Lesions can occur singly, be numerous or overlap to produce a single large lesion and appear polycyclic (several overlapping circular lesions).

Tinea cruris

The rash is usually isolated to the groin and inner thighs, but can spread to the buttocks. It is often bilateral and is normally intensely itchy, reddish brown and has a well-defined edge.

Tinea faciei

Fungal infections on the face are rare and are consequently often mistaken for other facial skin conditions. The lesions are similar in appearance to tinea corporis in that they will normally have a sharp well-defined border, show scaling and be itchy. Conditions such as acne, rosacea and lupus need to be considered in its differential diagnosis.

Tinea manuum

Tinea manuum is often misdiagnosed as eczema or psoriasis due to its atypical tinea appearance. The patient usually suffers from chronic diffuse scaling of one palm. Often athlete’s foot will be present, as the infection has spread to the hands from the feet due to the patient scratching their feet. The condition is not common and if no foot involvement is implicated then the diagnosis strongly points to dermatitis.

Psoriasis

Isolated fungal body lesions can be difficult to distinguish from plaque psoriasis. However, if the patient has psoriasis there will normally be a family history of psoriasis and the lesions tend not to itch, exhibit more scaling and do not show central clearing.

Dermatitis-allergic and contact forms

Both fungal infections and dermatitis exhibit red itchy lesions and therefore can be difficult to distinguish from one another. Patients with dermatitis will often have a family and personal history of dermatitis or be able to describe an event that triggered the onset of the rash. Misdiagnosis of a fungal infection for dermatitis and subsequent treatment with a steroid-based cream will diminish the itch, redness and scaling but the infecting organism will proliferate. On withdrawal of the steroid cream the visible signs of the infection will return and be worse than before, often in a papular form (tinea incognito).

Discoid eczema

This presents as round, raised, coin shaped lesions that particularly affects the arms and legs. It can itch and show superficial scale. It occurs mainly in middle aged people.

Allylamines

Terbinafine has been exempt from POM control in the UK since 2000. It inhibits the biosynthesis of ergosterol – an essential component of fungal cell membranes. Reviews have shown terbinafine to have high cure rates, slightly better than the imidazoles (Crawford & Hollis 2007).

Benzoic acid

Benzoic acid acts by lowering intracellular pH of dermatophytes and is combined with salicylic acid (Whitfield’s ointment). Although Whitfield’s ointment has been on the market for nearly a century it still has a role to play as an effective antifungal, but newer products, with higher cure rates, quicker resolution and more cosmetically acceptable formulations have replaced its widespread use in Western society.

Imidazoles

Imidazoles, like allylamines, act by inhibiting ergosterol production but at a later stage in the ergosterol biosynthesis pathway. They have largely replaced benzoic acid, undecenoates and tolnaftate, because they have greater efficacy and an excellent safety record (Crawford & Hollis 2007). There appears to be no clinically significant differences in cure rates between the different imidazoles and treatment choice will probably be driven by patient acceptability and cost.

Griseofulvin

Griseofulvin (as a 1% spray) works by inhibiting cellular mitosis. It has proven effectiveness when taken orally but has only limited trial data as a topical formulation. One trial reported an 80% mycological cure rate after 4 weeks with once daily application (Aly et al 1994).

Tolnaftate

Tolnaftate is thought to work by distorting fungal hyphae. It appears to have the least amount of trial data supporting its efficacy. Low patient numbers involved in the studies further compounds the difficulty in assessing its efficacy.

Undecenoates

The exact mechanism of action for undecenoates is not understood. They have been used to treat athlete’s foot for over 30 years and features in the most recent United States Pharmacopoeia. In a recent Cochrane review, undecenoic acid was said to be efficacious in treating fungal infections for skin and nail infections of the foot (Crawford & Hollis 2007).

Summary

On current evidence, an imidazole or terbinafine would be first-line treatment for superficial fungal infection. Both have similar mycological and symptom cure rates, although terbinafine might be preferred because it clears symptoms in a shorter space of time, although it is more expensive.

Imidazoles

All topical imidazoles have excellent safety records and can be used by all patient groups, including pregnant and breastfeeding women. They do not have any drug interactions and the major side effect associated with their use is irritation on application. To prevent reinfection, imidazoles should be used after the lesions have cleared, although, the length of time varies from product to product.

Tolnaftate (e.g. Mycil, Tinaderm, Scholl Athlete’s Foot Powder, liquid & cream)

Products containing tolnaftate have no interactions or side effects and can be used by all patients. They can be used for athlete’s foot and infections of the groin and should be used twice a day with treatment continuing for at least 1 week after the infection has cleared up.

Undecenoates (e.g. Mycota)

Products containing undecenoates have no interactions and can be used by all patients. They are licensed for athlete’s foot and should be used twice a day and treatment continued for at least 1 week after the infection has cleared up. Local irritation has been reported.

Benzoic acid (e.g. Whitfield’s ointment)

Benzoic acid (in combination with salicylic acid) is now rarely used. However, it is a safe medicine and can be used by all patients.

Terbinafine (Lamisil range & Scholl Advance Athlete’s Foot Cream)

Terbinafine can be used to treat athlete’s foot, groin infection and tinea corporis. The cream should be applied once or twice a day whereas the spray and gel should be used only once daily. It has no interactions, has few reported side effects and can be used by all patients. All products are licensed for people aged over 16, except Lamisil Once, which is for use in people aged over 18 years of age.

Griseofulvin (Grisol AF spray)

Licensed for athlete’s foot, Grisol should be applied to the area once daily. Each spray delivers 400 µg of griseofulvin with a maximum of three sprays in 24 hours for more extensive or severe infection. The spray should be used for 10 days after the lesions clear to prevent reinfection. It has no interactions, has few reported side effects and can be used by all patients.