Papulosquamous eruptions


Introduction

Papulosquamous eruptions comprise a group of disorders characterized by the presence of superficial papules and scale. These conditions account for a large number of patients in both pediatric dermatology and pediatric primary-care practice. In disorders of keratinization (psoriasis, pityriasis rubra pilaris, keratosis follicularis, ichthyosis, hyperkeratosis of the palms and soles, and porokeratosis), cutaneous lesions develop as a result of either genetically programmed retention or increased production of scale in the epidermis. In the inflammatory dermatoses (dermatitides, pityriasis rosea, pityriasis lichenoides, lichenoid dermatoses, and fungal infections), clinical findings result from epidermal response to dermal inflammation. An algorithmic approach to diagnosis for the papulosquamous disorders is summarized at the end of the chapter (see Fig. 3.55 ).

Disorders of keratinization

Psoriasis

Psoriasis is a common disorder characterized by red, well-demarcated plaques with a dry, thick, silvery scale ( Fig. 3.1 ). The condition affects 1–3% of Americans, of whom an estimated 40% develop the eruption before the age of 20 years. Psychosocial impairment in addition to physical symptoms make early diagnosis and intervention critical in children and adolescents.

Fig. 3.1, Psoriasis. (a) Typical erythematous plaques are topped by a silver scale on the trunk of an adolescent. (b) Thick, tenacious scale extends from the forehead, neck, and ears onto the scalp of this 10-year-old girl. (c) Thick plaques on the palms, soles, elbows, and knees of this 8-year-old boy caused severe pain when he attempted to walk or use his hands. (d) Another boy with an impressive plantar keratoderma had difficulty walking. (e) Widespread guttate lesions erupted on the trunk and extremities of this healthy 9-year-old boy 1 week after a streptococcal pharyngitis. (f) Disseminated guttate lesions also developed on this 13-year-old girl after an upper respiratory infection.

Psoriasis is a multifactorial disorder with both hereditary and environmental components. In more than one-third of patients, other family members are affected. A number of human leukocyte antigen (HLA) (e.g. HLA Cw6) types have been associated with psoriasis in different populations. Several genetic loci have been under investigation, and studies suggest a major susceptibility region for early-onset psoriasis on chromosome 6p21.3. Although the factors that initiate the rapid turnover in epidermal cells, which contributes to psoriatic plaques, are unknown, upper respiratory tract viral and streptococcal infections, urinary tract infections, and other infections are known to precipitate outbreaks in genetically predisposed individuals. Triggers of psoriasis also include drugs (interferon, lithium, carbamazepine, indomethacin, beta-blockers, terfenadine, terbinafine, isotretinoin, antimalarials), climate, cigarette smoking, alcohol, psychologic stress, and malignancy. Once the process is initiated, keratinocytes within the epidermis, under the influence of Th1 cytokines and cells of the immune system, amplify the psoriatic cascade, resulting in angiogenesis, hyperproliferation, and altered cell differentiation.

Cutaneous lesions tend to locate on the scalp, the sacrum, and the extensor surfaces of the extremities. About 50% of children present with large plaques over the knees and elbows. Thickening and fissuring of the skin of the palms and soles (keratoderma) may also be present ( Fig. 3.1 c,d). In one-third of children, many drop-like lesions (guttate psoriasis) are scattered over the body, including the face, trunk, and extremities ( Fig. 3.1 e). In infancy, psoriasis may present as a persistent diaper dermatitis. In older children, the eyelids, genitals, and periumbilical areas are commonly involved ( Fig. 3.2 ). Scalp disease may develop as an isolated finding but is often seen with other variants ( Fig. 3.1 b). Itchy, red plaques with thick, tenacious scale are often evident at the frontal hairline and around the ears. Nail changes, which may also occur as the first manifestation of psoriasis, include onycholysis (separation of the nail plate from the nail bed to produce “oil drop changes”), nail pitting, yellowing, increased friability, and subungual hyperkeratosis (see Fig. 8.58 a,b).

Fig. 3.2, These lesions were present on the (a) eyelids, (b) penis, and navel of this 8-year-old boy for 6 months before (c) he developed widespread papules and plaques on his arms and legs. (d) This 11-year-old girl had a persistent periumbilical plaque for over a year.

Of psoriasis patients, close to 10% suffer from psoriatic arthritis, one of the seronegative spondyloarthropathies. In half of these individuals, arthritis develops before the skin rash. Examination of the joints characteristically demonstrates heat, pain, and swelling of multiple joints of the hands and feet, particularly the distal interphalangeal joints. The arthritis tends to be progressive with the development of flexure deformities and contractures. In addition to the typical lesions of plaque psoriasis, patients often demonstrate severe psoriatic involvement of the hands, nails, and feet ( Fig. 3.3 ). The HLA B-27 antigen is usually positive.

Fig. 3.3, Psoriasis and psoriatic arthritis were debilitating in this adolescent girl.

Rarely, children develop erythrodermic psoriasis with acute widespread erythema and scaling or pustular psoriasis with generalized erythema and pustule formation ( Fig. 3.4 ). These variants are associated with high fevers, chills, arthralgias, myalgias, and severe, cutaneous tenderness. Fluid and electrolyte losses and leukocytosis may be marked. Secondary bacterial infection and sepsis can occur.

Fig. 3.4, Pustular and erythrodermic psoriasis. (a,b) Generalized pustulation developed suddenly within psoriatic plaques on this 8-year-old child. Skin lesions were associated with fever, chills, and arthralgias. (c) Erythroderma appeared in another 8-year-old girl with psoriasis. She also complained of chills, pruritus, and fatigue.

Psoriatic lesions are often induced in areas of local injury, such as scratches, surgical scars, or sunburn, a response termed the Koebner or isomorphic phenomenon ( Fig. 3.5 ). In areas of thick scale, tortuous capillary loops proliferate close to the surface. Gentle removal of the scale results in multiple, small bleeding points, referred to as the Auspitz sign ( Fig. 3.6 ).

Fig. 3.5, Koebner phenomenon in psoriasis. Pruritus was severe in this child who developed linear plaques in excoriations.

Fig. 3.6, Auspitz sign. Removal of the thick scale from a psoriatic plaque produces small points of bleeding from underlying tortuous capillaries.

The diagnosis is usually made by identifying the typical morphology and by the distribution of skin lesions. Confirmatory skin biopsy findings include regular thickening of the epidermal rete ridges, elongation and edema of the dermal papillae, thinning of the epidermis overlying tortuous dermal capillaries, absence of the granular layer, parakeratosis, spongiform pustules of Kogoj, and Munro microabscesses. In children, skin biopsies may not always be diagnostic, particularly in early disease and certain anatomic sites such as the keratoderma of the palms and soles.

The course of psoriasis is chronic and unpredictable, marked by remissions and exacerbations. A number of different topical agents, which include lubricants, corticosteroids, tar, dithranol (anthralin), and keratolytics, are useful in managing cutaneous lesions. Topical calcipotriol (and other vitamin D3 analogs), tazarotene (a member of the acetylenic class of retinoids), and topical corticosteroids with ultra-high potency may also play a role in the treatment of thick, localized plaques in some children. Occlusive dressings and pulsed-dye laser, which targets tortuous vessels at the base of psoriatic plaques, may be useful in localized disease. Disseminated, chronic or recalcitrant disease may require ultraviolet (UV) light therapy (broadband UVB 290–320 nm, narrowband UVB 311–313 nm, psoralen photosensitizer plus UVA [PUVA] 320–400 nm). Where available, narrowband UVB light therapy has replaced broadband UVB and PUVA in children because of improved safety and efficacy comparable with PUVA. Life-threatening erythrodermic and pustular psoriasis and psoriatic arthritis usually respond to oral retinoids (acitretin) and antimetabolites (methotrexate). Cyclosporine, an immunosuppressant that inhibits T-cell activation has been approved for use in adults with severe psoriasis and may be useful in children with severe, recalcitrant, disfiguring, incapacitating, or life-threatening disease. Recent studies with systemic tacrolimus and pimecrolimus have also shown these agents to be highly effective, but further data are needed on long-term safety. Both calcineurin inhibitors are also available in a topical formulation that may be effective for treating selective patients with facial and intertriginous (inverse) psoriasis. The use of systemic agents requires close laboratory and clinical monitoring.

A relatively new group of pathogenesis-based treatments capable of selective disruption of the psoriatic cascade show promise for management of severe disease in children. Apremilast is a small molecule inhibitor of phosphodiesterase 4, and the anti-tumor necrosis factor agents (adalimumab, etanercept, and infliximab), interleukin (IL)-17 signaling blockers (brodalumab, ixekizumab, and secukinumab), anti-IL-23 (guselkumab, risankizumab, and tildrakizumab), and the monoclonal antibodies directed against IL 12–23 pathway (ustekinumab) have been shown to be effective in adults. Because safety and efficacy data of these various classes are accumulating for the treatment of psoriasis in pediatric patients, the American Academy of Dermatology and the National Psoriasis Foundation issued joint recommendation guidelines for the management and treatment of psoriasis in this special cohort in late 2019. Etanercept and ustekinumab are U.S. Food and Drug Administration (FDA) approved for patients with psoriasis 4 years and older and 12 years and older, respectively. Recently, the manufacturers of ixekizumab received FDA approval for the treatment of the pediatric cohort from ages 6 to 18 with moderate to severe plaque psoriasis. In Europe, etanercept and ustekinumab along with adalimumab are also approved. Several other biologics are used off-label both here and abroad.

Pityriasis rubra pilaris

Pityriasis rubra pilaris (PRP) is an uncommon disorder of keratinization characterized by small follicular papules, widespread orange-red, scaly plaques surrounded by islands of spared skin, and marked thickening of the skin on the palms and soles ( Fig. 3.7 and Fig. 3.8 ). Onset of disease occurs most commonly in prepubertal children and in adults over 50 years old, and it has been associated with trauma, acute, self-limited illness, and immunocompromised states such as HIV. Most cases are sporadic and acquired, but a familial variant has been reported. Overall, 75% of cases resolve spontaneously within 3–4 years, but in familial disease, persistence is the rule.

Fig. 3.7, Pityriasis rubra pilaris. (a) Discrete hyperkeratotic follicular papules on the trunk and extremities of this 10-year-old girl progressed over several weeks to give confluent plaques. (b) Note several discrete areas of sparing on the abdomen and arm flexures.

Fig. 3.8, Pityriasis rubra pilaris. This child developed a salmon-colored keratoderma of the (a) soles and (b) palms.

In childhood, the circumscribed variant, which accounts for a majority of the cases, begins with the development of coalescing hyperkeratotic papules on the elbows and knees and a palmoplantar keratoderma ( Fig. 3.8 ). Superficial, red, scaly plaques occasionally appear on the face and trunk. Less commonly, children develop a pattern that mimics the classic adult variety. The eruption begins with follicular, hyperkeratotic patches on the back, chest, and abdomen, which expand to involve interfollicular skin. Lesions on the scalp and other sebaceous areas develop simultaneously or soon thereafter and may disseminate. Even in widespread disease, islands of normal appearing spared skin are characteristic. Discrete, hyperkeratotic papules may also remain present over the knuckles, wrists, elbows, and knees. In erythrodermic PRP, facial edema and scale may result in ectropion formation. Nail dystrophy with subungual hyperkeratoses may also be present.

The clinical presentation, particularly with keratoderma of the hands and feet and follicular papules, helps differentiate PRP from psoriasis, seborrheic dermatitis, atopic dermatitis, and pityriasis rosea. A skin biopsy that demonstrates interfollicular orthohyperkeratosis and perifollicular parakeratosis is typical, but not diagnostic.

Although PRP is usually self-limited in childhood, severe disabling disease may require systemic therapy with retinoids or methotrexate. Variable response to therapy has been reported with topical vitamin D analogs, phototherapy, and systemic immunosuppressive agents including steroids, cyclosporine, and azathioprine. Recently, there has been increasing clinical experience with the systemic biologic agents in adults and children with this disorder (see section on psoriasis).

Keratosis follicularis (darier disease)

Keratosis follicularis is an autosomal-dominant disorder that typically presents in children from 8 to 15 years old and is characterized by hyperkeratotic follicular papules on the face, scalp, neck, and seborrheic areas of the trunk ( Fig. 3.9 ). Although the onset is usually insidious, a rapidly progressive course may follow an inciting event, such as intense sun exposure or a viral infection. Red, scaly papules coalesce to form widespread, thick, odoriferous, greasy plaques, particularly on the scalp and forehead and around the ears, shoulders, mid-chest, and mid-back. Flexures may also be involved, with moist vegetative plaques.

Fig. 3.9, Keratosis follicularis. Hyperkeratotic follicular papules erupted progressively on the trunk and face of this 9-year-old girl. (a) Some of the most prominent lesions are demonstrated on her shoulder. An adolescent demonstrates almost confluent papules on the (b) chest and an associated keratoderma on his (c) feet. (d) Asymptomatic confluent pebbly papules on the tongue of this 20-year-old man were noted with magnification.

Other characteristic lesions include flat-topped, warty papules on the dorsum of the hands and tiny hyperkeratotic papules and pits on the palms and soles. Subtle pebbly papules on the oral mucosa may simulate leukoplakia. Nail dystrophy, with thickening or thinning of the nail plate, fracture of the distal nail plate, longitudinal white and red streaks, and subungual hyperkeratosis, may also be present.

The genetic defect in Darier disease has been mapped to chromosome 12q23–q24.1, which results in dysfunction of an endoplasmic reticulum Ca 2+ ATPase (SERCA2) and subsequent disruption of intracellular Ca 2+ signaling. Although the cause is unclear, there is also a predisposition to certain bacterial, viral, and fungal infections. The tendency of affected individuals to develop disseminated herpes simplex (Kaposi varicelliform eruption) and recurrent staphylococcal infections has been recognized for years.

The characteristic clinical picture permits easy differentiation of Darier disease from other papulosquamous disorders, such as seborrheic dermatitis, PRP, and psoriasis. Classic histologic changes from skin biopsy, which include dyskeratosis (with the formation of corps ronds and corps grains), suprabasal acantholysis (leading to the formation of suprabasal clefts), and the formation of villi by upward proliferating dermal papillae, confirm the diagnosis.

Although Darier disease tends to persist throughout life, many patients experience episodic flares and remissions in disease activity. Topical vitamin A acid may be helpful in managing early lesions. However, its use is limited by a high risk of irritation. Experience with oral retinoids has been promising, but prolonged use may be associated with unacceptable complications, which include hyperostosis, epiphyseal plate changes, increased skin fragility, and teratogenicity. Aggressive protection from the sun and treatment of secondary bacterial and viral infections also control exacerbations.

Ichthyoses

The ichthyoses are a heterogeneous group of scaling disorders characterized by retention hyperkeratosis (ichthyosis vulgaris, X-linked ichthyosis) or increased proliferation of epidermal cells (lamellar ichthyosis, epidermolytic hyperkeratosis). These diseases may be differentiated by clinical findings, histopathology, biochemical markers, and specific genetic mutations, as outlined in Chapter 2 .

Palmoplantar keratoderma

Keratoderma is a heterogeneous group of disorders of keratinization defined by the presence of focal or generalized thickening of the skin of the palms and/or soles. Although difficult to characterize, keratodermas can be classified based on whether they are acquired or inherited, isolated or associated with other cutaneous or systemic findings, and specific morphologic features and extent of involvement of lesions on the palms and soles ( Table 3.1 ). Inherited keratodermas can be subdivided based on the mode of inheritance, presence of other ectodermal and non-ectodermal findings, and specific genetic and molecular markers. The astute clinician can often make a specific diagnosis by searching for key findings in the Online Mendelian Inheritance in Man database supported by the National Library of Medicine and the Johns Hopkins University School of Medicine.

TABLE 3.1
Variants of Palmoplantar Keratoderma
Type Disorder Genetics Onset Involvement Hyperhidrosis Associated Findings
Diffuse palmoplantar keratoderma Unna–Thost syndrome
  • Autosomal dominant (1:200–1:40 000); varies with ethnic group KRT1(keratin)1 chromosome 12q 13.13 KRT16 17q 21.2 chromosome

Infancy Palms, soles Severe
  • Occasional deafness, rarely total

  • Anomalous pulmonary venous return

Keratoma hereditarium mutilans (Vohwinkel syndrome)
  • Autosomal dominant (rare)

  • Recessive variant with ectodermal dysplasia

  • Mutation in connexin 26 and loricrin gene on chromosome 1q21.3

Infancy Honeycomb keratoderma; star-shaped plaques on hands and feet, elbows, knees ±
  • Digital constriction band; deafness; alopecia

  • May be associated with diffuse epidermolytic hyperkeratosis

Mal de Meleda keratoderma
  • Autosomal recessive

  • Mutation on chromosome 8q24.3 SLURP1 gene

Infancy Palms, soles, elbows, knees, including dorsal surfaces (transgridiens) ±
  • Flexion contractures; constriction bands; koilonychia; diffuse ichthyosis

Tylosis (Howel–Evans syndrome)
  • Autosomal dominant

  • Linked to chromosome 17q25

Adolescence Soles, sometimes palms ±
  • Esophageal carcinoma; epidermal cysts; thin lateral eyebrows, follicular papules

Papillon–Lefèvre syndrome Autosomal recessive
Mutation on 11q14.2
Birth to 2–3 years Soles more severe than palms, intense erythema, wrists, ankles, elbows, knees; follicular hyperkeratoses ± Nail dystrophy; periodontitis; calcification of falx cerebri; mental retardation; arachnodactyly
Olmsted syndrome
  • Autosomal dominant?

  • X-linked recessive?

  • Defect in keratins 5,14

Infancy Progressive, diffuse involvement of hands, feet, leads to flexion contractures, digital amputation (Anhidrosis) Periorificial hyperkeratosis
Oral leukokeratosis
Focal palmoplantar keratoderma Punctate palmoplantar keratoderma Autosomal dominant (2–5% African Caribbean individuals) Childhood, adolescence Palms, soles Variable
Tyrosimia type II (oculo-cutaneous tyrisonosis, Richner–Hanhart syndrome) Autosomal recessive 16q22.2 Infancy through adulthood Fingertips, palms Corneal ulcerations; mental retardation
Porokeratosis palmar, plantar, and disseminated 1 Autosomal dominant (rare) Childhood through adulthood Extremities, trunk Squamous cell carcinoma, increased with immuno-suppression

Unna-Thost (non-epidermolytic type), the most common genetic variant, is inherited in an autosomal dominant pattern and is associated with a defect in type 1 and type 16 keratins. This keratoderma presents in the first year of life with diffuse hyperkeratosis restricted to the palmar and plantar surfaces ( Fig. 3.10 ). Although lesions may be asymptomatic, hyperhidrosis may lead to maceration and the formation of painful fissuring, blisters, and bacterial superinfection. Unna-Thost must be differentiated from a number of unusual keratodermas associated with hyperkeratoses that extend to the dorsal surfaces of the hands and feet, elbows, and knees and develop at distant sites ( Fig. 3.11 ).

Fig. 3.10, Progressive hyperkeratosis began on the palms and soles of this father and toddler son by 3 months of age.

Fig. 3.11, Olmsted syndrome. Severe scarring keratoderma of the palms and soles was associated with perioral and perigenital hyperkeratosis, hyperhidrosis, recurrent cutaneous infections, and poor growth in this 5-year-old girl. Treatment with oral retinoids resulted in some decrease in the palmar and plantar lesions.

Focal keratoderma with discrete papules and plaques on the palms and soles also appears as an isolated phenomenon or in association with other cutaneous findings and systemic disease. A mild autosomal-dominant variant with pits and hyperkeratotic papules in the hand and foot creases occurs in 2–5% of black individuals ( Fig. 3.12 ). Occasionally, this keratoderma is painful and requires surgical treatment.

Fig. 3.12, Focal keratoderma. Asymptomatic hyperkeratotic papules and pits (a) developed on the hand creases of an African American teenager. Painful punctuate papules and pits began in adolescence on the palms and (b) soles of this young man similar to lesions on his father, uncle, grandfather, and several siblings.

Neurosensory deafness, carcinoma of the esophagus (Howel–Evans syndrome), and peripheral neuropathy (Charcot–Marie–Tooth disease) are rarely associated with palmoplantar keratoderma and may be excluded by auditory screening and a careful family history.

Hyperkeratosis of the palms and soles that presents as part of a diffuse disorder of keratinization, such as psoriasis or PRP, is differentiated by a thorough examination of the integument for other diagnostic clinical findings. Unfortunately, it may be difficult to make a specific diagnosis until other features of the underlying disorder manifest.

Porokeratosis

Porokeratosis is a disorder of keratinization characterized by annular, sharply demarcated plaques with raised hyperkeratotic borders ( Fig. 3.13 ). Although many rare subtypes have been described, four distinctive variants are recognized, based on morphology and distribution of the lesions, time of onset, triggering factors, mode of inheritance, and, in some instances, specific genetic mutations.

Fig. 3.13, Porokeratosis. Porokeratosis of Mibelli on (a) the thumb, (b) the right hip, and (c) the chin. (d) This adolescent with disseminated superficial actinic porokeratosis began to develop asymptomatic nummular patches on his legs after a sunburn when he was 16 years old. Note the hyperkeratotic borders in all of the patients, which demonstrated a coronoid lamella on skin biopsy. All lesions were slowly progressive.

Porokeratosis of mibelli

Subtle, reddish-brown, scaly papules that slowly enlarge to form irregularly shaped plaques with hypopigmented atrophic centers and raised, grooved (double-edged) borders are typical of this condition, which invariably develops in childhood ( Fig. 3.13 a–c). Plaques are usually unilateral and vary in size from a few millimeters to several centimeters in diameter. One to three lesions are usually present. This rare, autosomal-dominant variant appears most commonly on the extremities, thighs, and perigenital skin, although any area that contains mucous membranes can be involved. Biopsies of the longitudinal furrow in the border demonstrate the diagnostic coronoid lamella, which consists of a parakeratotic column that fills a deep, epidermal invagination.

This variant has been associated with clonal chromosomal abnormalities in chromosome 3 in the region 3p14–p12. Chromosomal instability may rarely result in the development of squamous cell carcinoma within these slowly progressive lesions. Although excision or carbon dioxide laser surgery may be useful, recurrences have been reported.

Linear porokeratosis

This variant presents much like the Mibelli variant. However, plaques are linearly arranged on the distal extremities and trunk, where they demonstrate a zosteriform pattern. Onset is also in early childhood, but the mode of inheritance has not been established.

Disseminated superficial actinic porokeratosis

Disseminated superficial actinic porokeratosis (DSAP) is a common autosomal-dominant variant with delayed expression, found primarily in lightly pigmented individuals of Celtic extraction. Many small, 2–4 mm diameter, hyperkeratotic papules appear symmetrically on sun-exposed surfaces of the extremities during the second and third decades of life ( Fig. 3.13 d). These brown-, red-, or skin-colored lesions may coalesce to form irregular, circinate patterns. Progression of papules, which occurs particularly during the summer months, can be slowed by aggressive use of sun protection. A mutation in some families with DSAP has been identified at 12q23–24.1.

Punctate porokeratosis

Punctate porokeratosis affects the palms and soles and has been described as a distinct entity. However, it usually presents in association with the Mibelli or linear variant. Punctate porokeratosis may also occur as a widely disseminated form reminiscent of disseminated superficial actinic porokeratosis, but with involvement of both sun-exposed and sun-protected areas. It is included in the differential diagnosis of punctate keratoderma.

Inflammatory dermatitides

Many of these disorders demonstrate changes of both acute (erythema, edema, vesiculation, crusts) and chronic (scaling, lichenification, hypopigmentation, hyperpigmentation) inflammation. Microscopically, dermatitis is recognized by the presence of intercellular edema (spongiosis), variable epidermal thickening (acanthosis), and the presence of dermal inflammatory cells, usually lymphocytes. Research and development of a number of new medications designed to selectively inhibit the dermatitic inflammatory cascade have led to more specific understanding of the molecular basis of these disorders. Various dermatitides may be differentiated by clinical features and specific histologic patterns.

A reasonable way to think of these conditions is as exogenous (“outside job”) versus endogenous (“inside job”) phenomena. Exogenous disorders include irritant and allergic contact dermatitis and photodermatitis. Endogenous dermatitides include atopic dermatitis, dyshidrotic eczema, nummular dermatitis, and seborrheic dermatitis. Juvenile palmar and plantar dermatosis and perioral dermatitis are triggered by a combination of inside and outside factors. Pityriasis rosea and parapsoriasis present with distinctive dermatitic patterns, but their causes are unclear.

Contact dermatitis

Contact dermatitis refers to a group of conditions in which an inflammatory reaction in the skin is triggered by direct contact with environmental agents. In the most common form, irritant contact dermatitis, changes in the skin are induced by caustic agents such as acids, alkalis, hydrocarbons, and other primary irritants. Anyone exposed to these agents in a high enough concentration for a long enough period of time develops a reaction. The rash is usually acute (occurring within minutes), with itching or burning, well-demarcated erythema, edema, blister formation, and/or crust formation.

By contrast, allergic contact dermatitis is a T-cell–mediated immune reaction to an antigen that comes into contact with the skin. In the initial phase of the reaction, antigens are processed by Langerhans cells in the epidermis under the influence of keratinocyte-derived cytokines. T-cells subsequently migrate to regional lymph nodes where there is clonal expansion of the specifically sensitized lymphocytes. Elicitation of an allergic response occurs on subsequent exposure to the allergen with proliferation of T lymphocytes in the skin and regional lymph nodes.

Although contact dermatitis frequently presents with dramatic onset of erythema, vesiculation, and pruritus, the rash may become chronic with scaling, lichenification, and pigmentary changes ( Fig. 3.14 ). At times the allergen is obvious, such as poison ivy or nickel-containing jewelry. Often, however, some detective work or formal patch testing is required to elicit the inciting agent ( Fig. 3.14 f). The initial reaction occurs after a period of sensitization of 7–14 days in susceptible individuals. Once sensitization has occurred, re-exposure to the allergen provides a more rapid reaction, sometimes within hours. This is a classic example of a type IV delayed-hypersensitivity response.

Fig. 3.14, Allergic contact dermatitis. Allergic contact dermatitis as a result of the application of benzocaine demonstrates sharply demarcated, hyperpigmented, lichenified patches on (a) the neck and (b) the top of the hands. (c) The location of the rash helps determine the cause of a contact dermatitis, such as in this girl with a nickel allergy. (d) This child became sensitized to the elastic waistbands of his underwear. (e) An 11-year-old girl had a persistent itchy dermatitis for 6 months, which resolved after she started using a paper toilet seat cover at school. (f) This 9-year-old boy with a history of atopic dermatitis developed a chronic nickel contact dermatitis, which cleared when his parents switched him to a metal buckle-free belt.

The most common allergic contact dermatitis in the United States is poison ivy or rhus dermatitis, which typically appears as linear streaks of erythematous papules and vesicles ( Fig. 3.15 ). However, with heavy exposure or in exquisitely sensitive individuals, the rash may appear in large patches. When lesions involve the skin of the face or genitals, impressive swelling can occur and obscure the primary eruption. Direct contact with the sap of the plant (poison ivy, poison oak, or poison sumac), whether from leaves, stems, or roots, produces the dermatitis ( Fig. 3.16 ). Indirect contact, such as with clothing or pets that have brushed against the plant, with logs or railroad ties on which the vine has been growing, or with smoke from a fire in which the plant is being burned, is another means of exposure. Areas of skin exposed to the highest concentration of rhus antigen develop the changes first. Other sites that have received lower doses react in succession, which gives the illusion of spreading. However, once on the skin, the allergen becomes fixed to epithelial cells within about 20 min and cannot be spread further. Thorough washing within minutes of exposure may prevent or reduce the eruption. Barrier creams applied before exposure may afford some protection.

Fig. 3.15, Poison ivy or rhus dermatitis. (a) Crusted papules forming linear plaques were noted on the left side of the abdomen and left arm of this 11-year-old boy several days after a hike in the woods. (b) Similar lesions appeared on the face of this 7-year-old boy. (c) A 10-year-old girl developed intense facial edema after brushing against poison ivy. (d) In highly sensitized children, large blisters can develop. This child was swinging from vines in the woods.

Fig. 3.16, Plants that provoke dermatitis after direct contact with the sap. (a) Poison ivy has characteristic shiny leaves in groups of three; it may grow as a vine or low shrub or bush. (b) Poison oak also has leaves in groups of three, although the edges tend to be more scalloped than those of poison ivy.

Other common contact allergens include nickel, formaldehyde resin, wool alcohols, fragrance mix, and cobalt chloride. Several studies using standard patch-test techniques show that the prevalence of contact sensitivity to these allergens in children is similar to that of adults. Moreover, patch testing in children is safe and effective, and clinically significant findings may exceed 70% in carefully selected patients.

Some allergens, known as photosensitizers, require sunlight to become activated. Photocontact dermatitis caused by drugs (e.g. tetracyclines, sulfonylureas, and thiazides) characteristically erupts in a symmetric distribution on the face, the “V” of the neck, and the arms below the shirt sleeves. Topical photosensitizers (e.g. dyes, furocoumarins, halogenated salicylanilides, p-aminobenzoic acid) produce localized patches of dermatitis when applied to sun-exposed sites. These agents are found in cosmetics, sunscreens, dermatologic products, germicidal soaps, and woodland and house plants (see Chapter 7 ).

Occasionally, the local reaction in a contact dermatitis is so severe that the patient develops a widespread, immunologically mediated, secondary eczematous dermatitis. When the dermatitis appears at sites that have not been in contact with the offending agent, the reaction is referred to as “autoeczematization” or an “id” reaction ( Fig. 3.17 ).

Fig. 3.17, (a) An adolescent boy developed severe poison ivy contact dermatitis on his arms the day after a hike in the woods. (b) The next day a widespread, itchy eczematous papular eruption appeared on his trunk and extremities.

A careful history usually reveals the source of contact dermatitis. In some patients, patch testing with a standardized tray of common antigens or the suspected antigen and several controls is necessary to confirm the diagnosis.

Although small areas of contact dermatitis are best treated topically, widespread reactions require and respond within 48 h to a 2- to 3-week tapering course of systemic corticosteroid; these begin at 0.5–1.0 mg/kg per day. Patients may experience rebound of the rash when treated with a shorter course. Oral corticosteroids may also be indicated in severe local reactions that involve the eyelids, extensive parts of the face, the genitals, and/or the hands, where swelling and pruritus may become incapacitating.

Atopic dermatitis

Also known as eczema, atopic dermatitis is a chronically recurrent, genetically influenced skin disorder of early infancy, childhood, and occasionally adult life. Although it was initially described in the nineteenth century, it was not until 1935 that Hill and Sultzberger first characterized the clinical entity. The term atopy , derived from the Greek word that means “not confined to a single place,” was introduced in 1923 by Coca and Cooke to describe a cohort of patients with asthma and allergic rhinitis who demonstrated immediate wheal and flare reactions upon skin testing with a variety of environmental allergens. The sera of these patients contained skin-sensitizing antibodies that were subsequently characterized as IgE immunoglobulins. It was later recognized that these atopic individuals also frequently manifested the itchy, eczematous dermatitis that was labeled atopic dermatitis.

The term eczema , which means “boil over,” is used by many physicians when referring to atopic dermatitis. However, most dermatologists use the word eczematous as a morphologic term to describe the clinical findings in various sorts of acute (erythema, scaling, vesicles, and crusts) and chronic (scaling, lichenification, and pigmentary changes) dermatitis. Both acute and chronic dermatitis may be present in atopic patients at different sites at the same time and the same site at different times during the course of the disease.

Although data are not precise, recent surveys reveal that atopic dermatitis is rather common with an incidence of 10% among Americans. The prevalence is highest among children, affecting 15–20% of all children between 6 months and 10 years of age. Subtle findings may be present during the first few months of life, and nearly 60% of patients have an initial outbreak by their first birthday. Another third develop disease between 1 and 5 years. The onset of eczema in adolescence and adulthood is unusual and should alert the clinician to the possibility of other diagnoses.

In families with a history of allergic rhinitis or asthma, nearly one-third of the children are expected to develop skin lesions of atopic dermatitis. Inversely, in patients with atopic dermatitis, one-third are expected to have a personal history of allergic rhinitis or asthma, with two-thirds showing a family history of these disorders. Half of those who manifest the dermatologic condition in infancy or childhood ultimately develop allergic respiratory symptoms. Atopic dermatitis appears to be linked to the histocompatibility locus antigen (HLA-DRB1), as has been described in allergic rhinitis. Still, it seems to be inherited as an autosomal trait with multifactorial influences.

Many external factors, which include dry skin, soaps, wool fabrics, foods, infectious agents, and environmental antigens, act in concert to produce pruritus in susceptible individuals. The resultant scratching leads to acute and chronic changes typical of atopic dermatitis.

The pathogenesis of inflammation is unclear, and no single factor has been implicated in the initiation of the inflammatory cascade. However, there is evidence that expansion of type 2 cytokine-secreting lymphocytes plays a major role in the acute phase of atopic dermatitis ( Fig. 3.18 ). This results in increased levels of proinflammatory cytokines such as IL-4, -10, and -13, and of IgE and a corresponding decrease in interferon-gamma. Inflammatory dendritic cells have also been shown to increase in atopic skin, which further fuels inflammation and the itch–scratch cycle.

Fig. 3.18, In genetically predisposed individuals, external factors including environmental irritants and allergens, bacteria, fungi, viruses, and foods trigger the differentiation of Th2 lymphocytes from Th0 lymphocytes and the release of acute inflammatory mediators (interleukin (IL)-4, -5, -13, -31). In chronic disease, Th1 lymphocytes are activated and chronic inflammatory mediators are upregulated. Ig, Immunoglobulin.

In a subset of atopics, defects in barrier function may play an initiating role. Mutations in the filaggrin gene are associated with the development of ichthyosis vulgaris and barrier dysfunction and an increased risk of developing atopic dermatitis. Predisposition to atopic dermatitis has also been associated with alteration in ceramide content of stratum corneum and disturbed maturation of lamellar bodies, which serve as water-retaining molecules in the barrier.

Although there is no one specific laboratory study or clinical finding in atopic dermatitis, over the years, clinicians and investigators have developed a series of major and minor diagnostic criteria ( Table 3.2 ). In addition to a history of pruritus, the distribution, morphology, and evolution of skin lesions in atopic dermatitis follow a characteristic pattern ( Fig. 3.19 ). The infantile phase begins between shortly after birth and 6 months of age and lasts about 2–3 years. Typically, the rash is composed of red, itchy papules and plaques, many of which ooze and crust. Lesions are symmetrically distributed over the cheeks, forehead, scalp, trunk, and the extensor surfaces of the extremities ( Fig. 3.20 ). The diaper area is usually spared.

TABLE 3.2
Diagnostic Criteria for Atopic Dermatitis
Major Criteria (All Required for Diagnosis) Common Findings (At Least Two) Associated Findings (At Least Four)
  • Pruritus

  • Typical morphology and distribution of rash

  • Personal or family history of atopy

  • Immediate skin-test reactivity

  • White dermographism

  • Anterior subcapsular cataracts

  • Ichthyosis, xerosis, hyperlinear palms

  • Pityriasis alba

  • Facial pallor, infraorbital darkening

  • Dennie–Morgan folds

  • Keratoconus

  • Hand dermatitis

  • Repeated cutaneous infections

Fig. 3.19, Characteristic distribution of lesions of atopic dermatitis in infancy, childhood, and adulthood. (a) In infancy, widespread lesions may be generalized, sparing only the diaper area. The head and neck, as well as the flexural and extensor surfaces of the distal extremities, are often severely involved. (b) In older childhood, lesions tend to involve the flexural surfaces of the upper and lower extremities, as well as the neck. With severe flares of disease activity, the rash may become more generalized. (c) In adolescents and adults, the eruption is often restricted to the flexural creases. In some patients, hands or hands and feet, may be most severely affected.

Fig. 3.20, Infantile eczema. (a) This infant has an acute, weeping dermatitis on the cheeks and forehead. Involvement of (b) the trunk and (c) the extremities with erythema, scaling, and crusting is evident. Note the severe involvement of the extensor surfaces of the leg and sparing of the leg crease. (d) Usually the diaper area is the only portion of the skin surface that is spared.

The childhood phase of atopic dermatitis occurs between 4 and 10 years of age. Circumscribed, erythematous, scaly, lichenified plaques are symmetrically distributed on the wrists, ankles, and flexural surfaces of the arms and legs ( Fig. 3.21 ). The ear creases and back of the neck are also commonly involved. These areas develop frequent secondary infections, probably as a result of the introduction of organisms by intense scratching. Although the eruption may become chronic and rarely generalized, remissions may occur at any time. Most children experience improvement during the warm, humid summer months and exacerbations during the fall and winter.

Fig. 3.21, Childhood eczema with lesions on (a) the arm, (b) the ankles, (c) the neck, and (d) the buttock creases.

Of children with atopic dermatitis, 75% improve by 10–14 years of age; the remaining individuals may go on to develop chronic adult disease. Major areas of involvement include the flexural creases of the arms, neck, and legs. Chronic dermatitis may be restricted to the hands or feet, but some patients develop recurrent, widespread lesions.

Nummular eczematous dermatitis

Although nummular eczematous dermatitis was initially described as distinct from atopic dermatitis, clinicians frequently use this term to describe the discrete, coin-shaped, red patches seen on many patients with atopic dermatitis ( Fig. 3.22 ). Lesions typically appear as tiny papules and vesicles, which form confluent patches on the arms and legs. Nummular lesions may be extremely pruritic, and they are difficult to treat, particularly during the winter months, when the incidence seems to peak.

Fig. 3.22, Nummular eczema. (a) An adolescent demonstrated the acute exudative round patches of nummular eczema. (b) The term nummular eczema is also used to describe the chronic circular patches on the extremities and trunks of atopic patients, exemplified by the patches on another adolescent.

Prurigo nodularis

Although chronic rubbing results in lichenification, and scratching in linear excoriations, individuals who pick and gouge at their itchy, irritated skin tend to produce markedly thickened papules known as prurigo nodules ( Fig. 3.23 ). Although prurigo nodularis is not specific to atopic dermatitis, many patients with these nodules also have an atopic diathesis, which manifests as allergic rhinitis, asthma, or food allergy. Frequently, other stigmata of atopic dermatitis are present as well. Prurigo lesions tend to localize to the extremities, although widespread cutaneous involvement is observed in some cases.

Fig. 3.23, Prurigo nodularis. Widespread lichenified nodules involve the trunk and extremities of an adolescent boy with severe atopic dermatitis. Nodules may be particularly resistant to therapy.

Follicular eczema

Although a few atopic patients present initially with a predominance of follicular papules, virtually all patients develop these 2–4 mm diameter follicular lesions sometime during their clinical course ( Fig. 3.24 ). Lesions are usually widespread on the trunk, but careful observation also reveals their presence on the extremities, particularly early in flares of disease activity. In children with chronic disease, discrete papules may be obscured by excoriations and lichenification, particularly in the flexural creases.

Fig. 3.24, Follicular eczema. In some patients, follicular papules may be the only manifestation of atopic dermatitis. These lesions also occur in many atopic patients during the course of their disease, as in (a) this adolescent with follicular papules on his thighs and legs and (b) a 10-year-old boy with lesions involving his hands and forearms.

Ichthyosis vulgaris

Although ichthyosis vulgaris (IV) is inherited independently of atopic dermatitis, hyperlinearity of the palms and soles typical of IV is a frequent finding in patients with atopic dermatitis. Moreover, discoveries of the filaggrin loss-of-function mutations causing IV and the prevalence of these defects in atopics have highlighted the potentiation of atopic dermatitis in IV-affected individuals ( Fig. 3.25 ).

Fig. 3.25, This 14-year-old boy had a history of atopic dermatitis and ichthyosis vulgaris associated with hyperlinearity of the palms and soles and coarse non-inflammatory scale on his legs.

IV, which is inherited in an autosomal-dominant pattern with an incidence of 1:250, is associated with a defect in profilaggrin that is converted into filaggrin, the major protein comprising keratohyalin. The severity of IV increases with decreasing levels of functioning filaggrin. Retained polygonal scales are usually evident on the distal lower extremities (see Fig. 2.34 ), but they may also show a generalized distribution. Xerosis associated with ichthyosis may contribute to the pruritus present in atopic dermatitis.

Keratosis pilaris

Although keratosis pilaris is often an isolated finding, it is commonly associated with atopic dermatitis and/or IV. Keratosis pilaris results from retention of scales in the follicular infundibulum, which clinically is characterized by horny follicular papules and erythema on the upper arms, medial thighs, and cheeks ( Fig. 3.26 ). Occasionally, more widespread papules appear on the back, buttocks, and legs.

Fig. 3.26, Two adolescent boys demonstrate the typical features of keratosis pilaris with dramatic horny follicular papules on (a) the extensor surfaces of the thigh and (b) the lateral aspect of the cheek.

You're Reading a Preview

Become a Clinical Tree membership for Full access and enjoy Unlimited articles

Become membership

If you are a member. Log in here