Skin

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8 Skin

George Millington, Nandu Thalange

Introduction

All children will have a condition affecting their skin at some time. Most conditions are acute and transient, such as the exanthem accompanying acute viral infections like parvovirus, rubella and measles (see Chapter 16). These skin manifestations serve as a useful diagnostic guide but may not require specific treatment. Some, such as atopic eczema, will be chronic and potentially debilitating without appropriate management. Still others will be permanent and require care of the skin lesion and also of potential complications such as the epilepsy seen with port wine haemangioma in Sturge–Weber syndrome (see also Chapter 14, p. 204).

Inflammation

Chronic skin inflammation is usually due to eczema, although more rarely psoriasis is the cause. Self-limiting acute inflammatory disorders are commonly due to allergic or hypersensitivity reactions. The distribution of the rash is often highly characteristic and suggests the diagnosis (Figure 8.1).

Figure 8.1 Distribution of rash in various skin conditions.

Atopic eczema

Eczema is often described as the ‘itch that rashes’. Itch and dryness are key components of atopic eczema. Secondary infection, usually with Staphylococcus aureus and streptococci, is common, and should be suspected whenever the skin is weeping and crusted (as in Case 8.1). Viral superinfection, such as with herpes simplex or varicella, may cause dramatic exacerbations with marked systemic upset – eczema herpeticum.

Eczema is the commonest skin complaint of childhood, affecting 10–15% of all children. Eczema is an inflammatory eruption, with erythema and papules or vesicles on a dry background. Secondary scaling and crusting occur commonly, progressing to lichenification in chronic cases. Although a chronic condition, 90% of cases remit by 15 years of age.

Case 8.1

A girl with a dry itchy rash

Jade, a 14-month-old girl, was taken to the GP because she was distressed, miserable and would not sleep. She had a longstanding dry itchy rash over the wrists, in front of her elbows, behind her knees, and behind her ears. Recently the rash had become vesicular with weeping and crusting. She had previously had episodes of wheeze with viral infections and a single episode of a red blotchy rash after eating egg. Her mother had asthma and her father suffered from seasonal rhinitis.

The ‘itch–scratch cycle’ is a key factor. Dry skin itches and the child scratches. The trauma of scratching releases inflammatory mediators, causing more itch and may also break the epidermal barrier and lead to infection. The distribution of the rash varies with age, the face, head and trunk being more commonly affected in young infants, while the extensor and flexural surfaces of the limbs are more commonly affected in older children. There is a genetic predisposition in many cases with a history of eczema or other atopic diseases in close family members.

Trigger factors are not always obvious but include secondary staphylococcal infection, over-washing with soap, stress resulting in scratching, or, occasionally, dietary allergens such as egg or cow’s milk protein.

Contact eczema or dermatitis is uncommon in childhood although an allergic causation should be considered. This may be obvious, as e.g. with nickel sensitivity when the rash is limited to the area in contact with nickel. Common culprits are watchstraps or earrings. In some cases, biological detergents, or lanolin, found in many emollient creams, may cause contact dermatitis.

Seborrhoeic dermatitis has overlapping features but it appears preferentially on the scalp with a yellowish greasy appearance, often with more scaling, and it usually appears early in infancy. Scabies can resemble eczema due to the combination of scratching and inflammation/superinfection.

Treatment:

Management involves:

• Attempting to reduce the itch by reducing bathing and avoiding biological detergents

• Wearing loose clothing (preferably cotton)

• Managing dryness with emollients, used in place of soap, and applied copiously to affected areas. Wet wraps may help to seal in moisture

• Reducing inflammation by application of topical steroids; use of the more potent creams and lotions should be restricted to short courses to reduce the risk of side-effects

• Calcineurin inhibitors (tacrolimus, pimecrolimus) are recommended as second-line treatment by NICE (NICE clinical guideline 57, December 2007). These anti-inflammatory agents are effective, and do not thin the skin, unlike steroids. The commonest side effect is stinging after application, which quickly disappears. They may increase vulnerabililty to infection, and should not be applied to broken or obviously infected skin. There is a theoretical risk that they may increase skin cancer risk, so ideally should not be applied to sun-exposed areas over an extended period, and should not be used in conjunction with ultraviolet light treatment

• Anti-pruritics, usually antihistamines, which may help reduce itch, especially at night when the sedative effect is also potentially beneficial for sleep

• Avoidance of known allergens, which include measures to reduce exposure to house dust mite where appropriate

• Treatment of infection due to bacteria with short courses of oral antibiotics. Long-term use of topical antibiotics in combination with steroids is associated with antibiotic resistance.

• Phototherapy with ultraviolet (UVB) light is beneficial in some cases. Typically, 15–30 treatments are required.

• Severe cases may merit the use of oral steroids, azathioprine or ciclosporin.

Seborrhoeic dermatitis

Seborrhoeic dermatitis is usually a mild inflammatory disorder affecting sebum-rich areas of the scalp, face and trunk. Infection with the yeast Malassezia furfur is implicated in the pathogenesis. Malasssezia expresses lipases which act on sebum, releasing inflammatory fatty acids, in addition to activating the alternative complement pathway. The resultant inflammation ranges from mild dandruff to severe erythroderma. Clinical features depend on the site of infection:

• Scalp: involvement manifests as scaling and inflammation with the appearance of dandruff, but it may progress to a red, scaly, weeping rash. The rash may extend around the ears and onto the forehead. In infants, scalp involvement has the classical appearance of cradle cap with thick yellow scale.

• Ears: The skin around the ears may ooze and crust, and the ears may swell.

• Face: The nasolabial folds and inner eyebrows are most commonly involved. Eyelid involvement (blepharitis) may be troublesome.

• Chest and back: well-demarcated scaly red patches are seen on the central part of the chest and between the shoulder blades.

• Flexures: flexural involvement affects moist skin folds, particularly the groin, axillae, abdominal flexures and under the breast. Groin involvement is especially striking in infantile seborrhoeic dermatitis.

Seborrhoeic dermatitis may be especially severe in HIV infection, due to the unchecked proliferation of yeasts.

Treatment of the scalp is with medicated shampoos. Skin involvement responds to combined steroid/antifungal creams. In severe cases, a course of oral itraconazole may be necessary.

Infantile seborrhoeic dermatitis is a benign self-limiting variant affecting infants. It usually occurs in the first 3 months of life. Despite the florid appearance of the rash, the child is well and in no discomfort, in contrast to eczema. Treatment with a topical combined antifungal steroid cream is effective. Cradle cap may be treated by bathing with olive oil or other emollients or using an antifungal shampoo.

Psoriasis

Although more common in adults, 25% of individuals affected by psoriasis develop their first lesions in childhood. Around 1–3% of children are affected. Usually it develops as round red raised papules or plaques with a silvery-grey scale. The scalp, elbows, knees, lumbosacral area and the extensor surfaces of limbs are most frequently affected and distribution is often approximately symmetrical (see Figure 8.1). Less commonly seen is the guttate form with multiple small drop-like lesions, which more commonly occurs in adolescents. Associations include nail discoloration and pitting and a form of polyarticular arthritis (see Chapter 6, p. 52). Simple treatment of psoriasis entails adequate use of moisturizers, and sun exposure. Medical therapy is primarily aimed at symptom control. The mainstays of treatment are topical vitamin D analogues (e.g. calcipotriol) and topical coal tar preparations supplemented by short courses of topical corticosteroids. Ultraviolet B treatment (narrowband or broadband) is used in short courses for more severe cases (over the age of 14 years). Second-line treatment consists of disease modifying drugs – methotrexate is used in the first instance; ciclosporin is an alternative, if it is not tolerated. Acitretin, or other vitamin A analogues, may be used in boys, but the teratogenic potential makes use in girls undesirable. Use of second-line agents precludes the use of UV therapy due to the potential risk of skin cancer. Biologic therapy with monoclonal antibodies is reserved for third-line treatment. NICE has approved the following agents: Etanercept, adalimumab, infliximab and ustekinumab for psoriasis.

Pityriasis rosea

Pityriasis rosea is a self-limiting inflammatory skin disease, common in adolescence. A large red patch on the trunk – the herald patch – is followed 48–72 hours later by numerous small oval, rose-pink macules or papules, with scaling. The lesions on the trunk commonly follow the lines of the ribs, giving a characteristic ‘Christmas tree’ distribution. A viral aetiology is likely, but unproven. The rash remits in 1–2 months. Troublesome itch may be alleviated with aqueous cream; otherwise no treatment is required.

Urticaria and angio-oedema

Urticaria (commonly known as ‘hives’) is a relatively common dermatosis, affecting over 20% of people at some point in their lives. It is three times more common in atopic individuals. Urticaria is characterized by short-lived erythematous, intensely itchy swellings, known as wheals. It is a consequence of histamine release by mast cells in the skin. Angio-oedema is a related condition, with larger non-erythematous swellings, usually of the lips, tongue or extremities. Histamine release may be triggered by allergy, exercise, physical pressure, and even sunlight (solar urticaria). Allergens can be environmental, in food, drugs, or secondary to infection. In the common idiopathic form of urticaria/angio-oedema, it is unusual to identify a trigger. This is by far the commonest situation in children. Blood tests or skin prick tests are usually fruitless. Treatment is with non-sedating antihistamines, such as ceterizine. Angio-oedema may affect the tongue or throat. This may be alarming to the patient, but is rarely life-threatening. This is in contrast to hereditary angio-oedema (usually due to C1 esterase inhibitor deficiency), in which attacks are usually severe.

For acute angio-oedema, a short course of prednisolone is usually advised. If severe, iv chlorpheniramine may be used, and in life-threatening angio-oedema, adrenaline is indicated.

Episodes of urticaria/angio-oedema usually last from a few days to a few weeks. By definition, urticaria lasting more than 6 weeks is deemed chronic, and allergy is rarely the cause.

Erythema multiforme

Erythema multiforme is an acute hypersensitivity reaction. An infectious trigger is common; particularly mycoplasma and herpes group viruses. Drugs may also cause erythema multiforme. In a half of the cases no cause is identified.

The rash is dramatic, with sudden onset of macules, vesicles and urticarial elements, but target lesions are the hallmark. Target lesions are red 1–2 cm macules with a discolored purpuric or bullous centre. Involvement of the palms and soles of the feet is common. Accompanying fever, arthralgia and malaise usually occur. Symptomatic relief with paracetamol is normally the only treatment required, although in severe cases steroids may be used. Resolution takes 2–6 weeks.

Occasionally, the rash may be severe and involves the eyes, oral and nasal mucosa and anogenital region – Stevens–Johnson syndrome. Stevens–Johnson syndrome is a severe condition, which, rarely, may be life threatening. Mycoplasma pneumoniae is not infrequent as a causative organism. Treatment comprises supportive care to maintain hydration, nutrition and comfort. Intercurrent mycoplasma infection should be sought and treated. Intravenous methylprednisolone or immunoglobulin may speed remission.

Erythema nodosum

Large, tender, red patches over the shins may accompany infection or inflammation. Erythema nodosum may also occur secondarily to drug sensitivity. The lesions appear in crops lasting a few days and they are usually associated with systemic symptoms such as fever, arthralgia and malaise. The commonest infectious precipitants are Streptococcus and Mycoplasma. Tuberculosis, sarcoidosis and inflammatory bowel disease are important causes.

Skin infections

Bacterial infections

Impetigo

Case 8.2

A boy with lesions around his mouth

Andrew, a 3-year-old boy, developed a single red spot by his upper lip. Within 2 days, similar lesions around his mouth and over his cheeks had become vesicular, then pustular, and finally crusted. Yellow serous discharge had given the lesions a golden hue and separation of some of the crusts had left a raw weeping area.

The golden crusts seen in Case 8.2 are typical of impetigo, caused by Staphylococcus aureus or sometimes Streptococcus. The rapid spread is facilitated by auto-innoculation of the infection by rubbing and scratching. Skin swabs should be taken, and ‘best-guess’ systemic antibiotics commenced (e.g. co-amoxiclav) until culture and sensitivity results are available. Recurrence is common, often due to persistent nasal carriage.

Viral infections

Herpes simplex

Infection with herpes simplex virus type 1 is ubiquitous in children. In a minority, it causes a severe acute febrile illness with gingivostomatitis. Painful ulceration of the buccal mucosa results in erosion and haemorrhage. Dehydration may occur as swallowing is painful, and thick secretions may build up in the mouth. Treatment is with analgesia, fluids, oral hygiene and oral aciclovir.

Secondary or recurrent herpes labialis results in tightly grouped painful vesicles (‘cold sores’), with crusting over the lips and perioral region, and may be treated with oral aciclovir.

Molluscum contagiosum

Case 8.3

A girl with lesions on her fingers

Gemma, a 5-year-old girl, was taken to her GP. She had had several small raised lesions on her fingers for many months. They were approximately 2–5 mm in diameter, raised, with a central dimple (‘umbilication’) and pinkish-grey in colour. There was no itch but one or two lesions had become red and tender before disappearing over a few days.

Molluscum contagiosum is caused by a poxvirus and spreads by auto-innoculation. Uncommonly, secondary infection may occur, causing spreading erythema and tenderness, but more usually the lesions are relatively asymptomatic, as in Case 8.3. Healing, sometimes preceded by an episode of inflammatory change, occurs spontaneously, often after 18 months to 2 years.

Viral warts

Warts are intra-epidermal lesions due to the human papilloma virus. They occur most commonly on the hands, where they form raised hyperkeratotic lesions 2-4 mm in diameter, and on the soles of the feet, where they become embedded by trauma, causing painful plantar verrucas. Two-thirds resolve within 2 years. Salicylic acid paste or cryotherapy with liquid nitrogen may accelerate resolution.

Fungal infections

There are two principal causes of cutaneous fungal infections of the skin in children – Candida and dermatophytes.

Candidiasis

In candidiasis, the skin is inflamed and erythematous with neighbouring satellite lesions – small red spots adjacent to the affected skin. Candidal infections usually affect moist areas such as the perineum or around the mouth, particularly in infants. Treatment is with a combination steroid/antifungal cream such as clotrimazole-hydrocortisone.

Dermatophytes

Dermatophytes cause a number of superficial fungal infections:

• Scalp ringworm (tinea capitis): well-circumscribed, itchy bald patches, with scaling causing scarring alopecia. Green fluorescence is commonly seen under ultraviolet light, depending on the infecting organism

• Ringworm (tinea corporis): itchy erythematous patches, typically originating in the groin or axillae, extend across the trunk

• Athlete’s foot (tinea pedis): the toe webs are usually affected with moist, white, ‘blotting-paper’ skin. The infection may extend over the sole of the foot, and occasionally, the nails are affected.

Diagnosis is made on skin scrapings or nail clippings. Treatment is with topical or oral imidazoles. Treatment of scalp ringworm is with a 4-week course of terbinafine (though unlicensed in children). Shorter regimes using terbinafine or itraconazole may be effective. Topical imidazoles are usually effective for tinea corporis and tinea pedis.

Scabies

Sarcoptes scabiei is a highly infectious 8-legged mite, less than 0.5 mm in diameter, which burrows through the stratum corneum to cause recurrent crops of intensely itchy erythematous papules and vesicles. Scratching leads to excoriation with weeping, crusting and secondary infection. Linear burrows are characteristic but are readily seen in only 10–20% of cases. Usual sites in infants are the head, neck, hands, feet and face and, in older children, finger and toe webs, axillae, flexures, wrists and genitals. Microscopy of skin scrapings reveals the mite if there is diagnostic doubt.

Treatment is with:

• Topical application of malathion or permethrin to the entire body (index case and all household members)

• Washing of all clothing and bedding.

Haemangiomas

‘Strawberry’ naevus

Case 8.4

An infant with a red swelling of the eyelid

Kerry, a 3-week-old infant, presented with a red swelling of the eyelid, first noticed by the parents 2 weeks beforehand. It had spread from pin-point size to involve most of the upper eyelid. The child was well, with a 1 cm raised red-purple swelling comprising a leash of small capillaries, which partially blanched on pressure.

The finding of a rapidly swelling telangiectatic lesion early in infancy (as in Case 8.4) suggests a ‘strawberry’ naevus. Strawberry naevi are present in up to 3% of babies and are especially common in preterm infants. The lesion appears at, or shortly after, birth. Lesions grow quickly, reaching a maximum size by 6–12 months of age, after which spontaneous involution begins. Complete resolution usually occurs by age 9–10 years, and there is usually no residual trace – except sometimes a patch of pale or slightly atrophic skin.

Complications, including erosion with secondary haemorrhage, and infection, occur in about 5%. Very large cavernous lesions may cause platelet trapping in the abnormal vessels, leading to thrombocytopenia and bleeding – the Kasabach–Merritt syndrome. Many haemangiomas respond favourably to propranolol. Steroids may be tried in resistant cases, but side effects are problematic. Pulse-dye laser may be used after infancy, if lesions are in difficult locations, such as the eyes, mouth and ears. Laser therapy is less effective after age 6 years.

Port wine stains

Port wine stains are flat, small-vessel, capillary haemangiomas present at birth. They are often a deep purple shade, and usually flat, but bulky lesions are occasionally seen. They may be quite disfiguring, particularly on the face. When found over the upper cheek and forehead they may be associated with an intracranial vascular malformation – Sturge–Weber syndrome – with epilepsy and learning difficulties (see Chapter 14, p. 204). Early laser therapy is recommended for port-wine stains to achieve the best cosmetic effect.

Alopecia

Alopecia – loss of hair – may be diffuse or patchy.

Diffuse hair loss

Growing or anagen hairs normally constitute 80–90% of scalp hair, with the remainder – telogen hairs – being shed. A number of factors may affect the normal hair cycle of hair growth and loss; however, because of the long duration of hair growth, the effects are apparent only 6–12 weeks after the initial trigger, when there is widespread hair loss and thinning, but not bald patches – telogen effluvium – when the majority of hairs are in telogen. Precipitants include stress and illness. Normal hair growth resumes within a few months.

Diffuse hair loss also occurs secondarily to hypothyroidism, with zinc deficiency, and after chemotherapy.

Patchy hair loss

Circumscribed areas of hair loss leading to bald patches are divided into scarring and non-scarring alopecia.

Alopecia areata

The alopecia areata described in Case 8.5 is the commonest cause of non-scarring alopecia in children. The marginal exclamation-mark hairs, where the base of the hair tapers towards the scalp, and which may easily be pulled out, are characteristic. Nail pitting may be seen. There is an association with autoimmune conditions such as vitiligo and hypothyroidism. The majority of children recover completely, and the value of treatment is uncertain, but where desired, intradermal steroid injection has been used.

Case 8.5

A girl with hair loss

Kirsty, aged 12 years, presented with hair loss, leading to circumscribed bald patches over her scalp. There was no scarring or inflammation. On inspecting the scalp with a hand lens, ‘exclamation-mark’ hairs were seen at the edge of some of the lesions.

It is important to differentiate alopecia areata from traumatic hair loss due to tight hair bands, and from other causes of alopecia such as ringworm, or tinea capitis (see above), which are characterized by scarring.