Chapter 57 Dermatology
Skin conditions are common in pediatrics. This chapter presents an introductory discussion of dermatitis, diaper rashes, cutaneous infections, infestations, papulosquamous disorders, and childhood exanthems. A discussion of acne and its treatment is included in Chapter 54. Clinical photographs are available in electronic atlases (e.g., the Johns Hopkins University Dermatlas, http://dermatlas.med.jhmi.edu/derm/index.cfm) or standard textbooks (see References at the end of this chapter).
DERMATITIS
ATOPIC DERMATITIS
ETIOLOGY
What Is Atopic Dermatitis?
Atopic dermatitis is the most common chronic pediatric skin disorder. It generally begins during infancy or childhood; 90% of affected patients present before 5 years of age. The diagnosis is made clinically, based on the presence of three or more of the following: typical morphology and distribution of lesions, pruritus, chronic relapsing course, and a family or personal history of atopic disorders.
EVALUATION
How Do I Recognize Atopic Dermatitis?
The appearance of lesions varies with age and racial background. Infants and toddlers, for example, often have involvement of the face, trunk, and extremities. During childhood, lesions are concentrated in flexural areas, such as the antecubital and popliteal fossae, wrists, and ankles. Adolescents exhibit flexural involvement but often develop lesions on the hands, face, and neck. In light-colored skin, lesions are erythematous, somewhat scaly or crusted papules, patches, or thin plaques. In contrast, in skin of color, erythema is less obvious, and lesions may appear gray. In addition, the eruption is more papular, and postinflammatory hypopigmentation or hyperpigmentation may be present.
TREATMENT
How Is Atopic Dermatitis Treated?
Although there is no cure, most patients can be managed effectively with the measures outlined in Boxes 57-1 and 57-2.
Box 57-1 Daily Measures to Control Atopic Dermatitis
Control Pruritus
♦ Apply an emollient as needed. Lotions work well, but ointments are the best moisturizers (often not well tolerated because of greasy feel).
♦ Use a mild, unscented soap or soap substitute for bathing.
♦ Use an additive-free detergent for laundering clothes.
♦ To the extent possible, wear cotton clothing next to the skin.
Box 57-2 When Atopic Dermatitis Flares
Reduce Inflammation
CONTACT DERMATITIS
ETIOLOGY
What Is Contact Dermatitis?
Contact dermatitis occurs when an antigen penetrates the epidermis and sensitizes T lymphocytes. On reexposure to the antigen, sensitized T lymphocytes release cytokines that produce an inflammatory response, usually within 12 to 24 hours. Most often, contact dermatitis in pediatric patients results from exposure to plant allergens. Other allergens include nickel (present in jewelry, belt buckles, and clothing snaps), potassium dichromate (present in some shoes), neomycin, thimerosal, or formaldehyde (used in topical medications) or balsam of Peru or other fragrances (used in perfumes or soaps).
EVALUATION
What Are the Signs of Contact Dermatitis?
Potent antigens, such as urushiol (present in poison ivy, oak, or sumac), typically cause an acute dermatitis that consists of vesicles, bullae, erythematous papules, and edema. New lesions continue to appear for several days. If untreated, the dermatitis may persist for 3 to 4 weeks. Weaker antigens (e.g., nickel) produce a subacute dermatitis characterized by erythema, scaling, and lichenification. The key to recognizing contact dermatitis is the observation that the eruption is limited to certain areas. Linear vesicles or bullae on exposed surfaces suggest exposure to plant allergens. Nickel dermatitis occurs at sites of contact with jewelry or below the umbilicus where there is contact with a belt buckle or clothing snap. An eruption on the dorsa of the feet raises suspicion of shoe dermatitis.
TREATMENT
How Is Contact Dermatitis Treated?
For a patient with localized dermatitis involving areas other than the face, a mid-potency topical corticosteroid (e.g., triamcinolone acetonide 0.1% or fluocinolone acetonide 0.01%) may be applied twice daily; low-potency preparations (e.g., hydrocortisone 1%) are ineffective. However, when more than 10% to 15% of the body surface is involved, as may occur in plant dermatitis, oral prednisone may be required. An initial dose of 1 mg/kg may be administered once daily, then tapered by 20% to 25% every 3 days to complete a 12- to 21-day course. Discontinuing therapy earlier may result in a return of symptoms. Other treatments also may be beneficial. When vesicles rupture, drying can be promoted by taking tepid baths or applying cool compresses or shake lotions (e.g., calamine). An oral antihistamine provides sedation that offers relief from itching. Topical anesthetics containing benzocaine and topical antihistamines (e.g., diphenhydramine) are best avoided because they may induce a contact dermatitis.
How Is Contact Dermatitis Prevented?
Prevention of further episodes is important. Those who have experienced plant dermatitis should learn to recognize and avoid poison ivy, sumac, and oak. When exposure may be unavoidable (e.g., during hikes or camping trips), wearing protective clothing or applying a barrier preparation, such as Ivy Block, may be useful. For those with nickel allergy, avoiding jewelry containing the metal is important. Patients who wear earrings, for example, are advised to use varieties with solid gold or surgical stainless-steel posts. Clothing snaps may be painted with clear nail polish or covered with cloth tape.
SEBORRHEIC DERMATITIS
ETIOLOGY
What Is Seborrheic Dermatitis?
Seborrheic dermatitis is an inflammatory disorder of the skin that involves areas of the body where sebaceous glands are concentrated. The cause is unknown, but the inflammatory response is dependent on the presence of the yeast Pityrosporum ovale. It occurs at times when sebaceous glands are most active (e.g., in infants until age 9 to 12 months and during adolescence).
EVALUATION
How Do I Recognize Seborrheic Dermatitis?
In infants, seborrheic dermatitis causes scaling of the scalp (“cradle cap”) or salmon-pink scaling patches concentrated in skin folds (e.g., retroauricular and axillary) and the diaper area. Adolescents and adults experience scaling of the scalp (“dandruff”) or erythematous, scaling patches in the eyebrows, behind the ears, and in the nasolabial folds.
TREATMENT
How Is Seborrheic Dermatitis Treated?
The site involved determines the type of treatment. In infants with cradle cap, shampooing, during which the scalp is scrubbed with a soft brush to physically remove scale, may be sufficient. If scaling persists, an antiseborrheic shampoo (e.g., one containing zinc pyrithione or selenium sulfide) may be substituted. Adolescents with scalp involvement may be treated with an antiseborrheic shampoo or one containing ketoconazole; if inflammation is present, an appropriate topical corticosteroid (e.g., a mid-potency lotion or solution) may be applied at bedtime or, if needed, twice daily. Lesions elsewhere on the body (e.g., the face) are treated with a low-potency topical corticosteroid (e.g., hydrocortisone cream 1% twice daily) or, in adolescents, with a topical antiyeast preparation (e.g., ketoconazole cream twice daily).
DIAPER RASHES
What Are the Most Common Forms of Diaper Rash and How Are They Treated?
Diaper rashes are a common problem in infants. The most prevalent forms are irritant (because of excessive wetness that reduces the skin’s ability to withstand frictional forces and enzymes in stool that act as irritants), candidal, and seborrheic. The clinical features and treatment of these forms of diaper rashes are summarized in Table 57-1.
Table 57-1 Manifestations and Management of Common Diaper Dermatitis
| Type | Clinical Manifestations | Treatment |
|---|---|---|
| Irritant | Convexities involved | Change diaper frequently |
| Erythema, superficial erosions | Apply barrier preparation (e.g., zinc oxide paste) | |
| If inflammation severe, apply hydrocortisone cream 1% bid | ||
| Candidal | Convexities and creases involved | Apply topical antiyeast preparation (e.g., nystatin, miconazole nitrate) |
| Erythema, scaling, satellite papules or pustules | ||
| Seborrheic | Convexities and creases involved | Diaper area: apply hydrocortisone cream 1% bid |
| Salmon-pink erythema, greasy scale | Scalp: shampoo hair and brush scalp to remove scale (if ineffective, use keratolytic shampoo) | |
| Involvement of other areas (e.g., scalp, retroauricular folds, neck folds, axillae) | ||
| Skin: apply hydrocortisone cream 1% bid |
bid, Twice daily.
BACTERIAL INFECTION (IMPETIGO)
ETIOLOGY
What Is Impetigo and What Causes It?
Impetigo is a bacterial infection of the skin. It occurs in two forms: crusted (or nonbullous) and bullous. The crusted form accounts for more than 70% of cases and is particularly prevalent in warm, humid climates. It results from infection with Staphylococcus aureus and, possibly, group A beta-hemolytic streptococci (GABHS). Bullous impetigo is caused by strains of S. aureus that produce an epidermolytic toxin, which damages intercellular adherence, causing a cleft high in the epidermis and the formation of fragile blisters that rupture rapidly.
EVALUATION
How Do I Recognize Impetigo?
Children with crusted (nonbullous) impetigo have erosions covered with a yellow or honey-colored crust that typically are located around the nares. In contrast, bullous impetigo is characterized by flaccid bullae and round, erythematous, superficial erosions surrounded by a rim of scale, the remnant of the bulla roof.
TREATMENT
How Is Impetigo Treated?
Children with impetigo are treated with an antibiotic active against both S. aureus and GABHS. If the infection is widespread or multifocal, an oral agent such as a first-generation cephalosporin (e.g., cephalexin) or dicloxacillin is prescribed for 7 to 10 days. If infection is localized, a topical antibiotic (e.g., mupirocin) is sufficient. For those with bullous impetigo, oral therapy with a first-generation cephalosporin or dicloxacillin is indicated.
FUNGAL INFECTIONS
TINEA CORPORIS
EVALUATION
How do I recognize tinea corporis? Tinea corporis is characterized by one or a few expanding erythematous, scaling annuli (rings) or thin plaques. The border is well defined and often more elevated and inflamed than the center. Central clearing is often but not always present. In some children, small pustules are present at the border or throughout the lesion. Although these clinical features generally permit a diagnosis, if uncertainty exists, a potassium hydroxide preparation will demonstrate the branching hyphae.
TREATMENT
How Is Tinea Corporis Treated?
For children with one or a few lesions, a topical imidazole (e.g., miconazole nitrate) or other suitable topical antifungal agent may be applied twice daily until the lesion resolves, typically within 2 to 4 weeks. In the occasional patient with numerous or very large lesions, an oral antifungal agent such as griseofulvin is required.
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