Dermatology

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12.1 Dermatology

Roderic Phillips, David Orchard, Mike Starr

Essentials

1 Look at the rash.

• Are there any blisters? Finding fluid-filled lesions greatly narrows the range of possible diagnoses.
• Is the rash red? Redness is from haemoglobin. Most red rashes blanch, i.e. the redness disappears with pressure. If not, the haemoglobin is outside the blood vessels giving purpura.
• Is the rash scaly? If so, the epidermis is involved in the disease process. The epidermis may be broken to give weeping, crusting or fissures (‘eczematous rash’), or it may be intact (‘red scaly rash’).

2 Examine all the skin including the anogenital region.
3 Do not ignore a skin condition even if unrelated to the emergency visit. You may not deal with it yourself but you can organise appropriate follow up for it.

Introduction

Approximately 65 000 children a year attend the emergency department (ED) at the Royal Children’s Hospital in Melbourne and about 15 000 of these have some skin findings relevant to their visit. For 4000 children (6%), skin findings are a primary reason for their visit. These figures are likely to be representative of other tertiary teaching hospital EDs in Australasia. Diagnosing and managing these children requires a careful history and astute observation, particularly focusing on the appearance, site and development of their rashes.

For children who present to the ED with the primary symptom in another organ, the physician has an opportunity to observe cutaneous signs of disease, which may be relevant or may be coincidental to the child’s presentation, for example, a 5-year-old boy (Fig. 12.1.1) who presents with gastroenteritis. You notice the mild comedonal rash on his forehead and recognise that this is unusual at this age. Examination shows that he is tall for his age and has inappropriate penile (but not testicular) growth. His hyperadrenergic state can be investigated and treated years before it might otherwise have been recognised.

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Fig. 12.1.1 Mild prepubertal acne on the forehead of a 5-year-old boy who presented with the unrelated problem of gastroenteritis. Examination and investigation confirmed that he had a variant of congenital adrenal hyperplasia requiring treatment.

The discussion of diseases in this chapter is based on the features of the presenting rash and follows the algorithm given in Essentials. Diseases are grouped under their main morphology, e.g. vesicular, papular, eczematous, or purpuric. Mouth, anogenital, hair and nail problems are considered separately.

Erythroderma and skin failure

Erythroderma is one form of skin failure and refers to any condition that causes most of the skin surface to become red, often with some degree of scaling. Skin failure is rarely taught as a concept but is analogous to failure of any other organ system. Skin failure refers to the inability of the skin to adequately perform its functions, such as fluid and electrolyte balance, temperature control and protection from infection. Any child presenting with extensive areas of skin pathology or skin loss has some degree of skin failure. This may be well tolerated in otherwise healthy children but may be life threatening, especially in infants and those children with associated disorders.

Children presenting with erythroderma will usually be found to have one of the following: atopic eczema (with or without secondary staphylococcal infection); an allergic reaction; or sepsis with toxin-mediated skin involvement. Less common causes include: psoriasis; pityriasis rubra pilaris; several forms of inherited ichthyosis; some other genodermatoses; and internal lymphoid malignancies. In 10–20% of children with erythroderma, no cause can be found.

Management

• The aim is to restore and maintain the core functions of skin. Many sensible management decisions can be made before the diagnosis is clear.
• Have a low threshold for admission to hospital.
• Restore skin-barrier function by using an ointment emollient frequently.
• Monitor temperature, as the child may readily become hypothermic or, less commonly, hyperthermic.
• Monitor fluids and electrolytes.
• Monitor cardiac output, particularly if the child has known cardiac pathology.
• Skin and/or systemic sepsis may have caused the skin failure or may be secondary to it. Temperature control may be affected, so fever may not be present. Have a low threshold for giving systemic antibiotics, particularly to cover Staphylococcus aureus and streptococcal species.
• Local or systemic pain relief may be required.
• Cease all non-essential drugs.
• Identify and treat the underlying cause.
• Manage any associated conditions (e.g. diabetes, renal failure, congenital heart problems, metabolic disorders).

Vesiculobullous rashes

Vesicles are usually caused by infections (herpes simplex virus, varicella zoster virus, enterovirus, tinea, scabies or impetigo) or contact dermatitis. Also, consider drug reactions, erythema multiforme and photosensitivity. Dermatitis herpetiformis is a rare cause of itchy vesicles and papules. Larger blisters occur with staphylococcal infections, tinea, erythema multiforme, Stevens–Johnson syndrome, immune-mediated blistering disorders, arthropod bites, contact dermatitis, fixed and bullous drug reactions, mastocytosis, burns or trauma.

Many vesicles and blisters are fragile and rupture easily. A vesicular disease may present with a number of shallow monomorphic erosions but no vesicles. A bullous disease may present with several larger shallow erosions with surrounding loose epithelium but no bullae. Vesicles present for more than a couple of days become cloudy and vesiculopustular.

Varicella (chickenpox)

Varicella is caused by infection with varicella zoster virus. It usually occurs in children less than 15 years of age, and is highly contagious. The incubation period is 2–3 weeks. The contagious period begins 2 days before the rash and continues until the lesions are crusted. Clinical disease begins with a fever and malaise but these are usually mild. Lesions on the skin appear initially as erythematous macules, rapidly becoming small vesicles and then crusting. Over the next few days, anything from a few to hundreds of lesions may develop, initially on the face and trunk and gradually spreading onto the extremities. Superficial ulcers may be seen on all mucosal surfaces. Itch is not always present but may be marked. Vaccinated children may develop attenuated disease with fewer lesions and without constitutional symptoms. Diagnosis is clinical but can be confirmed by serology or immunofluorescence of vesicular scrapings for varicella-zoster virus antigen. Complete resolution occurs in most children but some scarring is common.

Children with varicella usually remain systemically well and afebrile after the first few days. If persistent fever and malaise is present, search for complications. In previously well children, the most common complications are:

• Bacterial skin infection with group A Streptococci or Staphylococcus aureus. Look for bullous, indurated, spreading or cellulitic lesions. Treat with oral antibiotics.
• Central nervous system (CNS) dysfunction. Encephalitis, meningitis, transverse myelitis, Guillain–Barré syndrome or Reye’s syndrome (sudden onset of vomiting, coma and liver abnormalities) may occur. Cerebrospinal fluid (CSF) analysis, including polymerase chain reaction (PCR) assay for varicella-zoster virus DNA may be useful in suspected encephalitis.
• Pneumonia. Cough and respiratory distress begin a couple of days after onset of the rash.
• Cerebellar ataxia may appear as the rash is clearing and resolve within weeks.

In neonates, immunocompromised children and adolescents, varicella can be more severe and occasionally fatal.

Management

• Treatment of otherwise well children with varicella is supportive with bland emollients and oral antihistamine if necessary. If the child is unwell, look for secondary complications.
• Avoid aspirin or other salicylates because of the association with Reye’s syndrome.
• Treat secondary skin infection with cefalexin 30 mg kg−1 (max 500 mg) three times daily.
• Immunocompromised children should be treated with intravenous aciclovir 20 mg kg–1 per dose (2–12 weeks), 500 mg m–2 per dose (12 weeks–12 years), 10 mg kg–1 per dose (adult) 8-hourly given over 1 hour.
• Premature neonates (less than 1 month old) with varicella should be treated with intravenous aciclovir.
• Term neonates should be admitted, and treated with aciclovir if they have severe disease.
• Give zoster immune globulin to at-risk contacts (immunocompromised children, those on prednisolone 2 mg kg–1 day–1 or more, newborns of mothers who have varicella any time from 5 days before until 2 days after delivery). Give within 4 days of exposure (6 mL for adults, 4 mL for children 6–12 years of age, 2 mL for children up to 5 years of age).
• Exclude from school until all lesions are crusted.
• Offer varicella-zoster vaccine to non-immune contacts – the vaccine has been shown to prevent or attenuate infection if given within 5 days of exposure.

Zoster

Zoster is uncommon in childhood but can occur at any age, even in the neonatal period. It occurs in children who have previously had primary varicella infection. Zoster in a young child is usually associated with primary varicella having occurred in infancy. The primary infection may have been mild and may even have gone unnoticed because of maternally-acquired IgG.

Radicular pain may be the first symptom of zoster but pain is less common than in adults and may not be present. Vesicles on an erythematous background appear in one or more groups aligned in a dermatomal distribution, frequently with a striking midline cut-off. The affected area can be an isolated group of a few vesicles suggestive of herpes simplex virus infection. Alternatively, there may be extensive involvement of one or more dermatomes. Lesions continue to appear for a few days and then resolve over 2 weeks, generally without sequelae. Postherpetic neuralgia is very uncommon after childhood zoster.

Complications include generalised dissemination during the first week of the rash, sometimes with pulmonary or brain involvement. This can be seen in both normal and immunocompromised children. Zoster on the head is occasionally accompanied by an aseptic meningitis, which resolves fully without treatment. Zoster lesions on the tip of the nose imply involvement of the nasociliary branch of the ophthalmic nerve and may accompany ocular involvement including keratitis and conjunctivitis. Facial nerve palsy and ear involvement can occur (Ramsay Hunt syndrome).

Immunocompromised children are much more likely to develop zoster. In such cases, zoster may be severe, extensive and prolonged. Significant dermatomal scarring can result.

Management

• If the diagnosis is unclear, collect epithelial cells from the base and roof of the vesicles for immunofluorescence and viral culture. This is not ‘just a swab’ and it requires some persistence to collect enough cells.
• In an otherwise well child, the occurrence of typical zoster does not require investigation for underlying immunodeficiency states. However, unusually severe or extensive zoster should raise this possibility.
• If a child has underlying chronic illness or immunodeficiency, give intravenous aciclovir or oral famciclovir or valaciclovir. Oral antiviral agents can be considered in older adolescents but are not generally indicated in an otherwise well child as the risk of significant symptoms or post-herpetic neuralgia is very small.

Hand, foot and mouth disease

Hand, foot and mouth disease is one presentation of enteroviral infection, usually Coxsackie A16 virus. There may be a mild prodrome of fever, malaise and sore throat. Discrete vesicles about 6 mm in diameter on an erythematous base appear first in the mouth, sparing the lips and usually sparing the gingiva. One to 2 days later, 3–7 mm vesiculopustules on an erythematous base appear on the palms, soles and around the fingers and toes. Lesions are also often found on the buttocks. They are often greyish and oval rather than circular in shape. In some cases, the mouth, hands or feet may not be involved. Resolution occurs within a week. The incubation period is about 5 days and epidemics are common. Virus is excreted in the faeces for weeks and exclusion is not recommended. Supportive care leads to complete recovery.

Herpes simplex infection (HSV)

Herpes simplex infection in childhood is common. Intrauterine, intrapartum and neonatal infection are considered elsewhere. Primary herpes infection after the neonatal period may be either primary herpetic gingivostomatitis or primary cutaneous herpes simplex. In children with impaired immune function, HSV infection can present as indolent, slowly growing, irregular ulcers. Most HSV infections in children are caused by HSV-1, but HSV-2 may also cause gingival and cutaneous infection.

Primary cutaneous herpes simplex can present at any age. There may be a history of a family member with a recently activated herpes simplex lesion on the lip (‘cold sore’). However, the virus is ubiquitous and transmission more often occurs from an unknown source. At least 50% of the population have HSV-1 antibodies, and many of these have never had an obvious infection. Painful grouped vesicles on an erythematous base can appear at any site. Multiple lesions rupture, crust and coalesce into larger erosions with scalloped edges. There may be associated fever, malaise and lymphadenopathy.

Management

Management consists of the following;

• supportive care;
• bathing of crusts;
• analgesia;
• aciclovir is not routinely indicated unless risk factors for complications exist (e.g. underlying disease, immunosuppression).

Recurrent cutaneous herpes simplex can occur weeks or months after the primary episode. Recurrences usually get milder and less common with time but exacerbations can occur throughout childhood and later life (Fig. 12.1.2). Recurrences can lead to significant time off school. Antiviral prophylaxis may reduce the frequency and severity of recurrences, and should be used if recurrences are frequent or debilitating.

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Fig. 12.1.2 (A) This erythematous, slightly vesicular rash around the eye of a 4-year-old boy had appeared over 12 hours. Because his other eye was blind, he was treated with oral aciclovir. Immunofluorescence confirmed herpes simplex virus. (B) One day later.

HSV infection can involve the fingers, especially the thumbs and index fingers (herpetic whitlow). At these sites, the thick skin does not readily rupture and children present with painful, coalesced pustular collections, often misinterpreted as bacterial abscesses. Any history of ‘abscesses’ occurring at the same site on a finger on more than one occasion is suggestive of herpes simplex. Management includes taking a swab for immunofluorescence and viral culture to confirm the diagnosis, analgesia and supportive care.

Eczema herpeticum

Herpes simplex infection in children with eczema is quite common. It occurs in children with any severity of eczema including children with mild eczema under excellent control. Many cases are misdiagnosed either as an exacerbation of the eczema or as bacterial infection (Fig. 12.1.3). Grouped vesicles may be prominent, but more often vesicles are rudimentary or absent and the infection may present as a group of shallow 2–4 mm monomorphic erosions on an inflamed base. In more severe cases, evolution is rapid and large crops of vesicles can arise daily. Ulcers may coalesce into larger erosions with scalloped edges. The infected area may not be painful or itchy.

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Fig. 12.1.3 Eczema herpeticum. Typical monomorphic vesicles can be seen away from the central weeping area.

In an atopic child, a high index of suspicion is needed about any patch of skin where small erosions or crusts are present and not responding to standard eczema therapy with moisturisers and topical cortisone derivatives. One reason for the under diagnosis of this condition is that even without treatment, resolution usually occurs in 1–4 weeks. However, dissemination may occur, leading to multifocal and extensive erosions, malaise and secondary bacterial infection. In the past, disseminated eczema herpeticum had a significant mortality but this has declined with the recognition and aggressive treatment of secondary bacterial infections.

After complete resolution, recurrences may occur at the same or different sites, sometimes as often as every few weeks. Recurrences can be widespread and severe but usually decrease in severity over 1 to 2 years.

Management

• Clinical differentiation between herpetic and bacterial infection may be difficult; investigation and empiric treatment for both may be necessary.
• Collect epithelial cells from the base and roof of the vesicles for HSV immunofluorescence and viral culture. This requires some persistence to collect enough cells.
• Local stable disease in an otherwise well child requires regular observation but does not need antiviral therapy.
• Milder cases demonstrating progression or facial involvement can be managed with oral aciclovir.
• Admission to hospital and treatment with intravenous aciclovir (20 mg kg–1 per dose (2–12 weeks), 500 mg m–2 per dose (12 weeks–12 years), 10 mg kg–1 per dose (adult) 8-hourly should be considered for children with any of fever, multiple sites of cutaneous herpes infection, widespread eczema, eye involvement, immunosuppression or age less than 6 months.
• Secondary bacterial infection is common. Swabs for microscopy and culture are usually unhelpful. If there is any suspicion of bacterial infection, add intravenous flucloxacillin 50 mg kg−1 (max 2 g) 6-hourly or oral cefalexin 30 mg kg−1 (max 500 mg) three times daily. Soak to remove excessive crusts.
• Monitor for eye involvement, particularly scleral redness. If present, this should be managed with topical or systemic aciclovir, or both, and urgent review by an ophthalmologist.
• The underlying eczema can be treated with moisturiser or wet dressings until the herpetic scabs have been removed and then it is important to restart topical cortisone treatment.
• Antiviral prophylaxis may reduce the frequency and severity of recurrences and is often warranted in older children with recurrent eczema herpeticum.

Impetigo (school sores)

This is caused by Staphylococcus aureus or group A Streptococcus or both.

Non-bullous impetigo presents initially as small erythematous vesicles that rapidly rupture to form yellow-crusted lesions, commonly on the face.

Bullous impetigo is due to Staphylococcus aureus and presents as flaccid blisters on normal skin. Lesions are rounded and well demarcated and may be single, grouped or widespread. Their onset and spread may be rapid or occur over days. New blisters appear and existing blisters rupture to give shallow moist erosions that can be many centimetres in size. There is often loose epithelium and/or brown crusting peripherally and some degree of central healing (Fig. 12.1.4). In more chronic cases, lesions may appear annular.

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Fig. 12.1.4 Bullous impetigo in a 7-year-old girl.

Impetigo is often secondary to itchy conditions such as scabies infection (especially hand impetigo), atopic eczema and head lice.

Post-streptococcal glomerulonephritis may occur in the ensuing 2 months. Contrary to long-held beliefs, it now seems likely that chronic streptococcal impetigo may also be a precursor of rheumatic heart disease in communities where medical conditions are poor and skin hygiene is suboptimal.1

Management

• Swab for microscopy and culture if the diagnosis is unclear or in widespread or complicated disease.
• Bathe off crusts.
• Apply topical mupirocin 2% ointment 8-hourly if very localised, or oral cefalexin 30 mg kg−1 (maximum 500 mg) three times daily if extensive.
• Isolate the child from other children or from sick adults unless all lesions are covered or antibiotic treatment has commenced.
• Treat any underlying condition such as scabies or eczema.
• Blisters or erosions often continue to occur for a couple of days after antibiotic therapy. If new blisters continue to form after this time, they may be caused by resistant Staphylococcus aureus infection, or the child may have an immune-mediated blistering disorder rather than impetigo.
• Children with chronic impetigo should be examined for any signs of heart disease. Families should be aware that rheumatic heart disease may be delayed by some years in this setting. Older siblings are likely to have had chronic impetigo in the past and therefore to also be at risk of heart disease and should be examined.
• In any child with chronic impetigo where ongoing care may be suboptimal, review with urinalysis to monitor for glomerulonephritis is warranted. In other cases, families should be aware of the possibility of renal involvement.

Staphylococcal scalded skin syndrome

This is usually seen in younger children or children with renal impairment. It is mediated by an epidermolytic toxin released from an often insignificant staphylococcal focus (e.g. eyes, nose or skin). Fever and tender erythematous skin are early features. Exudation and crusting develop, especially around the mouth. Wrinkling, flaccid bullae and exfoliation of the skin are seen and can be extensive. Nikolsky sign is present (‘normal’ skin separates if rubbed). Blisters are very superficial and heal without scarring.

Management

• Admit to hospital. Monitor temperature, fluids and electrolytes if large areas are involved. Increase oral (or intravenous) fluids to increase toxin excretion. Give analgesia.
• Consider alternative diagnoses including Stevens–Johnson syndrome and toxic epidermal necrolysis. If the diagnosis is unclear, a skin biopsy will confirm the diagnosis by showing the split is in the granular layer in the upper epidermis.
• Flucloxacillin 50 mg kg–1 (maximum 2 g) IV 6-hourly if there is evidence of sepsis or systemic involvement.
• Look for a focus of infection. Drain any foci of pus if present.
• Handle skin carefully and use an emollient ointment.

Erythema multiforme

This is a specific hypersensitivity syndrome that occurs at any age, often preceded by facial herpes simplex virus infection. It is over-diagnosed in emergency departments. Most children diagnosed with erythema multiforme actually have urticaria, often with large lesions with annular or polycyclic borders. In erythema multiforme, the primary lesions are red papules, usually symmetrical and involving the forearms, palms, feet, face, neck and trunk. They can be found anywhere. There may be few or many lesions. At least some of the papules will form classical target lesions – these have an inner zone of epidermal injury (purpura, necrosis or vesicle), an outer zone of erythema and sometimes a middle zone of pale oedema (Fig. 12.1.5). These papules and target lesions are not migratory. The involvement of mucous membranes is common but unlike Stevens–Johnson syndrome, is limited to isolated patches. Most cases are caused by herpes simplex virus, including most of the cases that occur without prior symptoms. Drugs are an uncommon cause. Erythema multiforme does not evolve into Stevens–Johnson syndrome. They are different conditions.

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Fig. 12.1.5 Erythema multiforme target lesions.

Management

• Fluid maintenance.
• Analgesia if required.
• Apply emollient ointment to the lips, if needed.
• If the condition is recurrent, it is highly likely to be related to herpes simplex virus. Prophylactic aciclovir prevents recurrences and should be considered if recurrences are frequent, severe and affecting the quality of life.
• Prednisolone alleviates symptoms but probably prolongs the duration of the condition and may cause recurrence of herpes simplex virus infection.

Stevens–Johnson syndrome/toxic epidermal necrolysis

Stevens–Johnson syndrome and toxic epidermal necrolysis are believed by many to be variants of the one condition. Most cases are thought to be triggered by medications, especially antibiotics (sulfonamides, penicillins), anticonvulsants (lamotrigine) and non-steroidal anti-inflammatory drugs. Mycoplasma and other infections may be the cause in some children. Fever, myalgia, arthralgia, headache and other organ involvement are usually present as a prodromal illness for several days. The rash evolves suddenly, characterised by widespread blisters on an erythematous or purpuric macular background, often with extensive mucous membrane haemorrhagic crusting. Lesions are usually on the face and trunk or generalised rather than acral, and typical target lesions are not seen. There may be tender erythematous areas with a positive Nikolsky sign (‘normal’ skin separates if rubbed). Mucous membrane involvement can be extensive, severe and painful. Conjunctivitis, corneal ulceration and blindness can occur. Anogenital lesions can lead to urinary retention.

Management

• See general advice under ‘skin failure’.
• Admit to hospital. A multidisciplinary approach including dermatology, paediatrics, ophthalmology, surgery and paediatric intensive care is required. Good nursing care is paramount. In severe cases, nurse in a specialised burns unit.
• Apply emollient ointment to the skin, lips and anogenital areas – this may be required many times a day.
• Regular eye examination with specialist review is required. Topical steroid eye drops may be needed.
• Give IV immunoglobulin 2 g kg−1. Commence ciclosporin (5–6 mg kg−1 day−1 orally for a few days, then taper to 3–5 mg kg−1 day−1 for 2–3 weeks). Data about the efficacy of any treatment regimens are limited but are sufficent to justify treatment. Stevens–Johnson syndrome has a significant mortality and has a high rate of permanent visual scarring including blindness as well as other problems.
• Maintain good nutrition, with nasogastric feeding if needed.
• Intubation may be needed if the child is unable to protect the airway because of severe oropharyngeal involvement.

Note: Stevens–Johnson syndrome is not severe erythema multiforme. They are distinct conditions. Permanent sequelae are rarely seen in severe erythema multiforme and concurrent drug use is unlikely to be the cause. Skin lesion distribution and morphology are the best discriminating factors. Mucous membrane involvement can be seen in both conditions but is confluent in Stevens-Johnson syndrome.

Dermatitis herpetiformis

Dermatitis herpetiformis is an uncommon autoimmune blistering disease that may present at any age as itchy papules or vesicles. Rapid excoriation means that intact vesicles are rarely seen. Lesions occur on extensor surfaces of the limbs, buttocks, trunk and scalp. Most patients have gluten enteropathy (coeliac disease) and may have abdominal discomfort, diarrhoea or anaemia. Some degree of villous atrophy will be seen on small bowel biopsy in most cases, but coeliac disease is often asymptomatic at the time of presentation of dermatitis herpetiformis. Growth retardation has been reported with dermatitis herpetiformis, probably secondary to intestinal involvement.

Recurrence some years after successful treatment has been reported.

Management

• Perilesional skin should be biopsied for immunofluorescence to demonstrate the diagnostic granular IgA deposition.
• Investigate for coeliac disease with total IgA, anti-tissue transglutaminase IgA and anti-deamidated gliadin IgA. Anti-transglutaminase antibodies are the most specific for dermatitis herpetiformis. A small bowel biopsy is required but may be equivocal early in the disease course.
• Anaemia, usually megaloblastic secondary to malabsorption, may be found.

Skin lesions (but not intestinal symptoms) respond well to dapsone, but haemolysis and other side effects can limit its use. A gluten-free diet normalises gut function and, in most children, leads to eventual clearing of skin lesions.

Other immune-mediated blistering disorders

As with dermatitis herpetiformis, the many diseases in this group are characterised by circulating autoantibodies directed against one or other of the structural proteins that give the epidermis its integrity. All are uncommon in childhood, linear IgA dermatosis (chronic bullous disease of childhood) being the most common. An immune-mediated blistering disorder should be considered in an otherwise well child if vesicles, blisters, or crusted erosions continue to appear for more than a couple of weeks.

If there is a split below the basement membrane, lesions may be tense, long-lasting bullae, as seen in dermatitis herpetiformis, linear IgA dermatosis, systemic lupus erythematosus and pemphigoid. If the split is higher in the epidermis, lesions are flaccid, short-lived blisters that rapidly give crusted erosions with loose epithelium around the edges. These are seen in pemphigus variants. Lesions can mimic local or generalised impetigo. Mucous membranes may be involved. Despite the widespread and often dramatic appearance of the rash, the child is usually well. Accurate diagnosis always requires histology and immunofluorescence in addition to clinical findings. Management requires immunosuppressive therapy and long-term follow up.

Sunburn and photosensitivity

Excessive solar radiation to the skin causes erythema and tenderness commencing at least half an hour after the beginning of the exposure. Tenderness worsens for a day and resolves in 4 days. In more severe cases, oedema and blistering may be widespread. Healing is accompanied by desquamation and intense itch. Sunburn occurs more rapidly when the sun is overhead (summer, closer to the equator, 11 a.m. to 3 p.m.), and when the skin is less pigmented, but can occur with any skin type. Children with sensitive skin can burn significantly within 15 minutes of midday exposure in summer.

Any child presenting to the ED with sunburn or with a rash in sun-exposed areas may have an underlying photosensitivity disorder. These can be considered in four groups.

Primary photosensitivity disorders.
Inherited disorders including porphyrias.
Diseases with a photosensitive component (systemic lupus erythematosus, dermatomyositis).
Exogenous photosensitivity from drugs or plants.

A high index of suspicion is needed to diagnose photosensitivity. There have been examples of sunburn in children that were attributed to parental neglect but were actually due to a photosensitivity disorder. These diseases are common but diagnostic traps abound. For example, sun-induced rashes may develop in spring with the first sun exposure of untanned skin after winter, but not later in summer. The rash may develop on areas usually covered in winter such as the neck and arms and not on the face. Sun-induced rashes may require a few minutes or several days of sun exposure and may commence days after the exposure. In erythropoietic protoporphyria, sun exposure induces pain without skin changes initially. Viral exanthems may occur exclusively or mainly in areas of sun-exposed skin. Children with solar urticaria develop urticaria on sun-exposed areas.

Management

• Assess for associated causes (below) of increased sun sensitivity. Many children presenting to the ED with ‘sunburn’ have an associated photosensitive trigger. Any child who experiences symptoms within half an hour of sun exposure should be assumed to have an underlying condition.
• Assess the family situation, especially with younger children. Significant sunburn in a young child can occur in the setting of suboptimal child care, although usually it is due to an oversight by otherwise caring parents.
• Within the first few hours of exposure, before blistering has developed, application of topical potent steroid creams can considerably reduce the severity and duration of symptoms.
• Cool compresses and wet dressings will alleviate symptoms. Topical anaesthetics should not be used. Admission and oral analgesia may be required in severe cases. Maintain adequate fluid intake.
• Educate about prevention.

Prevention

Prevention of sunburn is important. Episodes of sunburn are linked to later development of naevi and melanoma.

Parents need to balance the psychological and physical benefits of activities associated with sun exposure (including increased fitness, increased independence, healthier bones and decreased obesity) with the increased risk of skin cancers of all types. In summer, children should minimise sun exposure during the middle 4 hours of the day, wear broad-brimmed hats and long-sleeved shirts in the sun, and use a sunscreen with SPF 30 or greater on exposed parts.

Sunburnt infants regularly present to the ED, partly because of widespread advice that sunscreens are not recommended below the age of 6 months. This recommendation is not based on any evidence of problems in infants. It is based on the premise that it is usually easy to protect young babies who can’t crawl by keeping them out of the sun and appropriately dressed. However, if a young baby is going to be in the sun, sunscreen should be used.

Primary photosensitivity disorders

Polymorphous light eruption (PMLE)

Presents in spring or early summer as skin-coloured or erythematous itchy papules or vesicles on the face, ears, neck or arms. It is recurrent. Recurrences usually occur at the same sites in that child.

Juvenile spring eruption

Is a specific variant of PMLE and is common in 4–12-year-old boys as a recurrent blistering of the ears each spring.

Hydroa vacciniforme

Is rare and can begin at any age in childhood as a sun-induced vesicular eruption on the cheeks during spring and summer. The cheeks, ears, nose, dorsum of the hands and rarely the eyes can be involved. Recurrences occur for many years.

Diagnosis can be difficult and may require formal evaluation in a photobiology unit including assessment of the response to different wavelengths of light. Management requires sun avoidance and often both UVA and UVB sun protection.

Solar urticaria

Presents as urticaria within minutes or hours of exposure and settles within 1 day. Sharp margins are seen at the edges of clothing. Skin chronically exposed to the sun, such as face and hands, is often spared.

Porphyrias and other inherited disorders with photosensitivity

The porphyrias are a group of inherited enzymatic defects in haem synthesis leading to increased levels of porphyrins, some of which cause photosensitivity.

Erythropoietic protoporphyria

Is the most common childhood porphyria. Infants and young children present after brief sun exposure with acute discomfort, burning sensations, itching, erythema, oedema, urticaria and occasionally vesicles, particularly on the face and dorsum of the hands. Episodes are recurrent and with time affected skin appears prematurely aged. Erythrocyte protoporphyrin levels are elevated.

Congenital erythropoietic porphyria

Is rare and presents in early childhood with extreme photosensitivity leading to painful blisters filled with red fluid on the face and dorsum of the hands. Progressive scarring can be severe.

Familial porphyria cutanea tarda

Presents in childhood with chronic blistering on hands, arms and face leading to poorly healing ulcers, atrophic scarring and mottled hypo- and hyper-pigmentation.

If a porphyria is suspected, measure blood, urine and faecal levels of porphyrins. Management requires intensive avoidance of solar radiation including UVA and UVB. β-Carotene is useful in erythropoietic protoporphyria.

Many genodermatoses including xeroderma pigmentosum, Cockayne syndrome, Rothmund-Thomson syndrome and trichothiodystrophies are associated with photosensitivity and increased photo-damage to skin, but do not usually present with blistering.

Photosensitivity and bullous reactions to drugs

Blisters may be the presenting feature of a number of different types of drug reactions. A high index of suspicion is required to diagnose these conditions. Families must be asked about all ingested and topical products including herbal, recreational and prescription drugs and unusual food patterns (e.g. daily cups of celery juice). Families will occasionally not remember the causative drug and deny taking anything, only to recall the vital information days later.

Many medicines can cause increased sun sensitivity leading to erythema, oedema and blistering on sun-exposed areas. Doxycycline (particularly at doses higher than 100 mg day–1

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