36 Dermatologic Disorders

Peggy Vernon, Margaret A. Brady, Nancy Barber Starr, Ann M. Petersen-smith

The skin is the body’s largest organ and one of its most important. The condition of the skin reflects physical and emotional health, plays a major role in defining identity and supporting survival, and often gives clues to underlying conditions. Skin functions are multiple. Beauty is often defined by the appearance of the skin. Emotions are expressed by blushing and sweating. Skin conveys many impressions through its sensory functions, including reaction to touch, heat, cold, pressure, and pain. Additionally, the skin provides a protective physiologic covering, the first line of defense against injury from chemical, physical, and microorganic invaders. Homeostasis is maintained through fluid regulation and thermoregulation.

Disruptions in the skin account for a significant percentage of all pediatric office visits. The primary care provider plays an essential role in maintaining skin integrity, identifying and minimizing skin disruptions, maximizing healing, and educating parents and children about skin care.

Skin development is constant from embryogenesis throughout life. During the embryonic period (the first 2 months of gestation), the skin differentiates into several layers. The skin changes and develops throughout childhood and adolescence, achieving adult skin thickness and characteristics in the late teenage years. Melanin in the skin reaches adult levels by 1 year of age. Vascularization is well developed by the end of the second year of life. Cutaneous nerves develop until puberty and beyond. Sebaceous glands cease production between 6 and 12 months of age, but become active again at around 7 years old. Eccrine sweat function begins between 2 and 18 days of age, although full function is not in place until 2 or 3 years old. The apocrine glands become active at puberty. Hair grows approximately 1 cm per month. Nails are spoon shaped and thin from infancy until 2 to 3 years old.

Anatomy and Physiology

The skin is composed of three layers: the epidermis, the dermis, and the subcutaneous layer (Fig. 36-1). Skin, including its epidermis and dermis, varies from 1.5 to 4 mm in thickness (Weston et al, 2007).

FIGURE 36-1 Structure of the skin.

(From Jarvis C: Physical examination and assessment, ed 2, Philadelphia, 1996, Saunders.)

The epidermis, the thinner outer layer, functions as a protective barrier between the body and the environment and is comprised of five layers of stratified squamous epithelium. Most epidermal cells are keratinocytes, and the replication and maturation of the keratinocytes is called keratinization. New keratinocytes of the basal layer mature and shed approximately every 28 days. The outer horny layer, the stratum corneum, is responsible for much of the barrier protection against microorganisms and irritating chemicals. It impedes the exchange of fluids and electrolytes with the environment and provides strength for the skin. Melanin protects deoxyribonucleic acid (DNA) from damage by ultraviolet (UV) light irradiation. It is produced in the basal layer of the epidermis and contributes to the color of the skin, eyes, and hair. The water content of the environment influences the epidermal barrier, with either excess or inadequate amounts contributing to microscopic and macroscopic breaks.

The thicker middle layer, the dermis, contributes strength, support, and elasticity to the skin. It is a tough, leathery mechanical barrier that also regulates heat loss, provides host defenses of the skin, and aids in nutrition and other regulatory functions. The dermis is primarily composed of fibrous connective tissue (made up of fibroblasts and collagen), with some elastic fibers and a mucopolysaccharide gel. It includes mast cells, inflammatory cells, blood and lymph vessels, and cutaneous nerves that elicit sensations (touch, pain, pressure, itch, warmth, and cold). These specialized receptors are a defense mechanism to protect the skin surface from environmental trauma.

Underlying the dermis is subcutaneous tissue primarily composed of adipose tissue. It contains arteries and arterioles that assist in skin thermoregulation. The subcutaneous tissue insulates, cushions against trauma, provides energy, and metabolizes hormones.

Skin appendages include the hair, nails, sweat glands, and sebaceous glands. Hair follicles are found over the entire body except for the palms, soles, knuckles, distal and interdigital spaces, lips, glans and prepuce of the penis, and areolae and nipples. Two types of hair can be found on the body. Terminal hair is thick and visible and found on the scalp, axillae, and pubis. Very fine vellus hair is found over the remainder of the body. The visible portion of the hair is the shaft. The hair root is embedded in the dermis as a pilosebaceous unit, consisting of a hair follicle and a sebaceous gland. The hair shaft may be straight, wavy, helical, or spiral. Following an acute febrile illness or stress, there may be hair thinning for several months.

Nails are epidermal cells converted to keratin that grow continually. The nailbed, underneath the nail plate, is composed of layers of epidermis and dermis, which serve as structural support. The nail root lies just under the epidermis.

There are three types of sweat glands. Eccrine glands are distributed over the entire body. They help maintain fluid and electrolyte balance and body temperature, and provide some excretory function. Ceruminous glands are located in the external ear canal and secrete a waxy pigmented substance, cerumen. Apocrine glands are located primarily in the axillary, genital, and periumbilical areas. They open into hair follicles, require androgens to stimulate their secretions, and are thought to be responsible for body odor.

Sebaceous glands, found in conjunction with hair follicles, are distributed over the entire body except the soles, palms, and dorsa of the feet and contribute to the epidermis protection. These glands secrete sebum (oil) when stimulated by androgen and function to prevent excessive water evaporation, minimize heat loss, and lubricate the skin and hair.

Pathophysiology and Defense Mechanisms

Disruption of the skin and subcutaneous tissue occurs through a variety of assaults. These include:

The skin’s outer layers provide the body’s first line of defense from chemical, physical, and microorganic injury. The epidermis provides a functional barrier, the dermis provides strength and protection through the cutaneous nerves, and the subcutaneous tissue ensures insulation, is a cushion to prevent injury, is an energy source, and functions in hormonal metabolism. These layers, in turn, protect the other body systems. The water content of the skin enhances the protective barrier of the skin. If the skin becomes too dry or too wet, breaks in the barrier elicit an inflammatory response. As a continuously growing system, the skin not only heals itself but controls growth or colonization of microorganisms by continual shedding.

There are three identified cutaneous reactions to trauma, infection, or inflammation: pigment lability, follicular response, and mesenchymal response. Pigment lability occurs as postinflammatory hypopigmentation or hyperpigmentation. If superficial, with changes in the epidermis only, normal pigmentation returns in about 6 months (e.g., in diaper rash, seborrhea, tinea, pityriasis alba). If dermal changes happen, dermal tattooing may occur, causing long-term or permanent changes (e.g., excoriated acne, impetigo, varicella, contact dermatitis). The exaggerated follicular response results in prominent papule and follicle formation, especially with atopic dermatitis, pityriasis rosea (PR), syphilis, or tinea versicolor. The mesenchymal response causes scars and keloids (that extend beyond the edge of the scar), often following varicella, ear piercing, burns, or any surgical procedure.

Special Dermatologic Considerations in Children With Dark Skin or from Diverse Cultural or Ethnic Groups

Knowledge of the normal variations in children both with different levels of pigmentation of the skin and from diverse ethnic or cultural groups is important for assessing and treating dermatologic conditions. Skin reactions to injury, inflammation, common skin conditions, and cultural practices are varied. A wise pediatric health care provider listens to parents because they are often the first to detect subtle changes in color or texture of the skin. This section discusses some of the dermatologic differences of children with dark skin.

Preventive care for patients with dark skin should be implemented in routine well-child care. The following are initial areas to include:

Cutaneous Reaction Patterns

Pigment lability is common and tends to be more obvious in dark-skinned individuals regardless of race. People of color are especially prone to the development of keloids and hypertrophic scars, sometimes from relatively minor skin trauma. Other exaggerated responses common in darker-skinned individuals include lichenification and vesicular or bullous reaction to bites or staphylococcal infection. African-American children may have an exaggerated cutaneous response to common disorders of the skin. Of note, erythema of inflamed black skin may be difficult to detect and may appear as a purplish tinge (Paller and Mancini, 2011).

Normal Variations and Common Problems

The following are normal variations or common problems in children with dark skin:

• Variation in color and texture of skin from one part of the body to another

• Pigmentation of gingiva, mucous membrane, sclerae, and nails correlates with degree of cutaneous pigmentation.

• Increased areas of melanin in thicker-skinned areas (elbow, knee)

• The term, Futcher’s or Ito line, describe the vertical line that separates the hyperpigmented dorsal and extensor surfaces from less-pigmented ventral surfaces. This line of differentiation follows Voigt lines and is most noticeable on the extremities.

• Mongolian spots and increased numbers of café au lait spots (see later discussion)

• Normal exfoliation produces a fine layer of gray scales.

• Color alterations (jaundice, anemia, cyanosis) are difficult to assess.

• Kinky, wooly, tightly curled hair with closely knit growth that tangles when dry and mats when wet

• Atopic dermatitis (see Chapter 24) with prominent follicular pattern with pityriasis alba and postinflammatory hypopigmentation

Cultural or Ethnic Practices with Skin Sequelae

Grooming, cosmetic, or healing practices of cultural or ethnic groups contribute to various conditions that may be seen. These include the following:

Assessment of the Skin and Subcutaneous Tissue

History

The history should assess the following:

• History of present illness

Onset and duration of present or recent illness (e.g., respiratory or gastrointestinal [GI])

Most common concerns: Pruritus, scaling, and alterations in cosmetic appearance

Symptom analysis—questions to ask about an eruption or lesions include:

• What did the rash or lesion(s) originally look like?

• How has it changed in appearance?

• Where did the eruption first begin, and has it spread to other locations (pattern of spread)?

• How long has the rash or lesion been present?

• Is the way it looks today typical of its appearance?

• Does the rash come and go?

• Has the lesion blistered, bled, or had discharge?

• Does it itch?

• What have you used to treat it and what was the effect?

What parts of the body are not affected by the rash or lesions (e.g., face, soles, or palms)?

Associated systemic symptoms: Fever, malaise, pain associated with lesion or eruption

Factors that alleviate or worsen skin symptoms or seem to trigger them

Exposures or allergies: Medication, foods, animals, plants? Known allergens? New substances? Persons with similar symptoms or illness? What soaps, hair products (shampoos, gels, pomade, etc.), lotions, and detergents are used?

All medication (prescription and over-the-counter) taken over the last few days, including creams, ointments, powders, or lotions (it is often helpful to have patients bring medications they have used to the appointment)

Prior incidents of similar rash

Recent travel

• Family review of systems

Similar symptoms

Skin disorders or history of atopy disorders (asthma, seasonal or drug allergies or atopic dermatitis)

Chronic illnesses with related dermatologic findings

• Client review of systems and past medical history

Usual state of health and recent illnesses

Skin, hair, and nails: Skin type (dry or oily), recent and long-term changes, previous incidence of skin disease

Eyes, ears, nose, and throat: Swelling, itching, crusting, discharge or circles around eyes, nasal mucus discharge, patency or irritation, dry mouth, lesions, or pain

Chest: Wheezing, coughing, or respiratory difficulty

Chronic illnesses with related dermatologic findings

Physical Examination

When seeing a child with a dermatologic condition, it is essential to assess whether the child is ill. This clinical impression helps the provider differentiate serious illnesses from the majority of dermatologic conditions. The entire body, not just exposed skin, needs to be examined. Attention should be given to the eyes, nose, mouth (mucous membranes, teeth), lymph nodes, and lungs because a skin disorder may be a cutaneous manifestation of other disease. The dermatologic examination includes a thorough look at the skin, scalp, hair, palms and soles, nails, and anogenital region.

Special techniques for examination of the skin may be required. Good light (daylight is best) is essential to a good examination. A source of direct light, such as a gooseneck lamp, is the best alternative. Other helpful tools include a magnifying glass, a ruler, a glass slide, and a Wood’s lamp (UV light). A glass slide gently pressed on the skin (diascopy) allows viewing of the skin with and without capillary filling. A Wood’s lamp is used to examine fluorescent-positive fungal infections and depigmenting skin disorders, such as vitiligo.

Identification of the type of lesion and correct use of terminology are essential to good dermatologic care. Essential documentation includes the following:

Primary skin lesions (Box 36-1) include changes that arise from previously normal skin. These descriptions should be memorized and used. Secondary skin lesions (Box 36-2) result from changes in primary lesions. Vascular skin lesions (Box 36-3) involve the blood supply. Other useful descriptive terms are listed in Box 36-4. Vesicles, pustules, scaling, and color changes should be noted when considering differential diagnoses.

BOX 36-1 Primary Skin Changes to Lesions

BOX 36-4 Descriptive Terms for Dermatologic Lesions

Acral—involving extremities (hands, feet, ears, etc.)

Annular—ring-shaped

Arcuate—arc-shaped

Circinate—circular

Confluent—running together

Contiguous—touching or adjacent

Diffuse or generalized—scattered, widely distributed

Discrete—distinct and separate

Eczematous—referring to vesicles with oozing crust

Grouped—arranged in sets

Guttate—small, droplike

Herpetiform—referring to grouped vesicles resembling those of herpes

Iris—arranged in concentric circles, one inside the other

Linear—arranged in a line

Localized—in a limited area

Nummular—coin-shaped

Pedunculated—having a stalk

Polycyclic—oval with more than 1 ring

Reticular—netlike

Serpiginous—snakelike, creeping

Symmetric—balanced on both sides

Target lesion—(iris or targetoid) erythematous papule or plaque characterized by a red to violet dusky center surrounded by a raised, edematous pale ring and red periphery

Telangiectatic—referring to dilated terminal vessels

Umbilicated—depressed or shaped like a navel

Verrucous—wartlike

Zosteriform—resembling shingles, following a nerve root or dermatome

Diagnostic Studies

A few simple laboratory tests are helpful in identifying or excluding dermatologic disorders. Proper procurement of the sample is important. Lesions can be scraped with a no. 15 blade or a toothbrush and scales or debris placed on a glass microscope slide or in culture material. The No. 15 blade is also useful for exfoliating a blister. It is important to scrape under any scabs to get a sample of the organisms. Moistening the lesion may facilitate this. Scrapings can be obtained from the edges of skin lesions, from plucked hair (getting the root is essential), from the nail plate, or from subungual debris. Laboratory tests that can be used include the following:

• Microscopic examination of skin scrapings:

Potassium hydroxide (KOH) can be used to examine for fungal disorders (hyphae or spores; Fig. 36-2). Scrape fine scales from the edge of the lesion onto a glass slide. Add a drop of KOH 20% to dissolve debris, and cover with a coverslip. Let sit for 20 to 30 minutes or heat gently (do not boil). Use × 10 magnification to examine.

Wright, Giemsa, or Gram stains are used to examine for bacteria or herpes simplex or herpes zoster (HZ) giant cells. Allow scrapings to air-dry, then stain with Wright or Giemsa stain. Use × 40 magnification to examine for bacteria.

• Tzanck smear for herpes, varicella, or zoster

• Microbial culture of lesions for bacteria, viruses, or fungi. Simple, inexpensive culture methods for fungal organisms include the dermatophyte test medium [DTM] and InTray CCD [includes Candida]. Skin or nail scrapings or hairs, including the root, are applied so that they break the agar surface. A color change is noted in 1 to 5 days.

• Patch or skin testing for allergic or contact reactions is usually done by dermatologists or allergists.

• Skin biopsy following local anesthesia may be by punch or shave method for any tumor, palpable purpura, persistent dermatitis, or blister that is not otherwise definitively diagnosed. Such procedures often require referral to a dermatologist.

• Complete blood count (CBC) and erythrocyte sedimentation rate (ESR) may evaluate infection or inflammation.

FIGURE 36-2 Fungal elements (hyphae) as seen on microscopic examination of a potassium hydroxide preparation.

(From Hurwitz S: Clinical pediatric dermatology, ed 2, Philadelphia, 1993, Saunders, p 374.)

Management Strategies

Hydration and Lubrication

Adequate skin hydration is essential to prevent and treat skin conditions. If the skin is overhydrated, the bonds between cells at the stratum corneum loosen and the barrier is broken. If the skin is too dry, it cracks, again breaking the barrier.

Bathing

Bathing is an efficient means of hydrating and lubricating the skin, especially with dry skin or in dry climates. Lukewarm, not hot, water should be used. The bath should last long enough for skin to become moisturized without becoming supersaturated or “pruned.” Bubble-bath solutions are especially irritating and should be avoided. Soaping and shampooing should be done at the end of the bath followed by thorough rinsing. The skin should be gently dried and a lubricating agent applied immediately. See Chapter 24 for further information on lubricating baths. Baths containing baking soda or colloidal oatmeal may help relieve pruritus. Bathing and other heat exposures can make a rash seem worse temporarily.

Environmental Considerations

Because water is essential to skin integrity, environmental humidity also plays a role. Excessive humidity (greater than 90%) or deficient humidity (less than 10%) can cause disruption of the skin. Macerated skin, for example, benefits from less humidity. Itching from excessively dry skin is often relieved by increased humidity provided by using a vaporizer or humidifier. In hot temperatures, itching can be alleviated by air conditioning. Water consumption also plays a role in maintaining proper skin hydration, and children should be encouraged to drink plenty of water.

Skin Care Agents

Medications

Topical treatments are most commonly used for dermatologic conditions. Topical therapy restores hydration, alleviates symptoms, reduces inflammation, protects the skin, reduces scale and debris, cleanses, and eradicates causative organisms.

Thought must be given not only to the medication used in treating skin conditions but also its preparation (Box 36-5) and vehicle (Fig. 36-3), including stabilizers, preservatives, and perfumes. Occasionally an individual is sensitive to a medication vehicle or preparation, and symptoms are aggravated rather than relieved. Common agents that cause sensitization include ethylenediamine, lanolin, parabens, thimerosal, diphenhydramine, propylene glycol, “caines,” and neomycin. The following guidelines for use of preparations may be helpful:

• Acute inflammation—wet dressings, powders, suspension lotions, alcohol- or water-based lotions, or aerosols

• Chronic inflammation—creams, oil-based lotions or gels, ointments

• Patient’s tolerance for and willingness to use certain vehicles

• Patient’s environment (dry or humid)

BOX 36-5 Preparations of Topical Medications

Creams—contain more water than oil and therefore are less occlusive; better used with less dry skin, in high-humidity areas, in summertime, and on parts of body that naturally cause occlusion (body folds); often accepted better by patient, but must be applied every 2 to 3 hours

Gels—alcohol based, provide good penetration of skin, but can burn on application; primarily used for acne and in hairy areas

Lotions—mixtures of powder and water, useful for drying, cooling, and soothing actions; emulsion lotions contain some oil, so are not as drying as lotions; lotions come in suspension or solution

Oils—fluid fats that hold medication to the skin as barriers or occlusive agents

Ointments—best used with dry skin; composed primarily of oil with little or no water; provide most potent concentration of medication because of their occlusive action on skin; generally need to be used only every 12 hours; tend to leave a greasy feeling and can cause heat retention from decreased evaporation

Pastes—made of a combination of powder and oil, which makes them somewhat difficult to apply and remove, but effective in providing dryness and protection for skin

Powders—absorb moisture and reduce friction, provide cooling, decrease itching, increase evaporation