CHAPTER 138

Papulosquamous Eruptions

Janice Ma, MD; Delphine J. Lee, MD, PhD, FAAD; and Ki-Young Yoo, MD

Rashes, a common problem in children, can be classified in ways that help to establish a diagnostic approach. First, rashes are assessed in terms of appearance: macular (flat), papular (raised), squamous (scaly), vesicular (fluid filled), or bullous (large, fluid filled). Next, the extent of the rash is determined. Rashes may be described as generalized or localized. Location is also important. The site of a localized rash may be consistent with certain diagnoses (eg, diaper dermatitis). Pruritus is an important distinguishing feature. Other systemic symptoms must also be taken into consideration. Rashes may be a primary skin condition or a manifestation of an underlying infection or reaction to a precipitating agent.

Papulosquamous eruptions are rashes characterized by scaly papules and plaques. Eczema is a broad group of skin disorders characterized clinically by scale and histologically by spongiosis and makes up a large component of the papulosquamous disorders. The etiology of many papulosquamous eruptions is unknown, and the clinical appearance of lesions is the reason they are classified together.

Epidemiology

Although a large number of conditions may cause papulosquamous eruptions in children, a select number of diagnoses account for most problems and are the focus of this chapter. One of the most common types of papulosquamous eruptions in children is atopic dermatitis. Atopic dermatitis has become increasingly more common, and the prevalence in school-age children in the United States is estimated to be between 10% and 20%. Positive family history is often elicited. The severity of atopic dermatitis generally improves with age; however, lifelong dry, itchy skin, in varying degrees of severity, is not uncommon. Seborrheic dermatitis is another common papulosquamous rash seen in the pediatric population. Although most commonly described in infants younger than 3 or 4 months, it can occur in all pediatric age groups. It is estimated to have a prevalence of up to 5%, encompassing pediatric and adult populations.

Scabies occurs worldwide and is frequently encountered in general pediatric and dermatologic settings. The prevalence is much greater in developing countries and in situations in which populations are forced into close proximity (eg, during wars, incarceration, in refugee camps). Scabies is transmitted through direct contact; thus, family members and close contacts are at greatest risk of infection.

Clinical Presentation

Papulosquamous eruptions consist of skin-colored to erythematous, scaly papules and plaques that may involve the face, trunk, or extremities. The lesions can be pruritic, and scratching may lead to crusting or secondary infection. Sometimes multiple family members are affected (Box 138.1). Chronicity and repeated manipulation may lead to lichenification (thickening) of involved skin.

Pathophysiology

The pathophysiology of atopic dermatitis has not been definitively established. Evidence suggests that mutations in the FLG gene, encoding a protein important for skin barrier function, may play a large role in atopic dermatitis. It is also important to keep in mind that atopic dermatitis is a multifactorial disease with variable expression, influenced by environmental factors. Inheritance of this disease is associated with atopy, made up of the triad of atopic dermatitis, allergic rhinitis, and asthma. The disorder is attributed largely to skin barrier function; however, immune dysfunction and reactivity of nerves and blood vessels may also be involved. Initially, the disease is characterized by Th1 cytokine predominance, but later in chronic disease, there is activation of the Th2 immune pathway with a resultant synthesis of cytokines, including interleukin (IL)-4 and IL-5, causing elevated immunoglobulin (Ig) E levels, eosinophilia, and diminished cell-mediated immunity. Elevated IgE is reported in up to 80% of patients with atopic dermatitis.

Like atopic dermatitis, the etiology of seborrheic dermatitis remains unclear. There may be an association with the yeast Malassezia, including the Malassezia furfur species (formerly known as Pityrosporum ovale), although whether this organism is causative is unclear. It is widely accepted that this yeast has some role in seborrheic dermatitis, which is further supported by the improvement observed with topical antifungal medications. Individuals with seborrheic dermatitis that is severe or extensive may have immune dysfunction, such as uncontrolled HIV/AIDS.

The inflammatory response in scabies is triggered by an infestation with the mite, Sarcoptes scabiei. The adult female burrows under the skin and lays 60 to 90 eggs. After 2 weeks, the eggs become adults. Affected individuals may be asymptomatic on first exposure. Up to 2 to 6 weeks after infestation, the host’s immune system becomes sensitized to mites or scybala (mite feces), resulting in systemic pruritus and rash. In most individuals, the rash associated with scabies is an allergic phenomenon; each eruptive papule may not actually contain mites.

Differential Diagnosis

While many papulosquamous eruptions are clinically distinguishable, the differential diagnosis may be challenging at times. Familiarity with the appearance of these conditions and their differentiating features is critical.

Conditions that present as papulosquamous eruptions in children include atopic dermatitis and seborrheic dermatitis, as described previously; however, the differential diagnosis is vast and includes other conditions, such as contact dermatitis, psoriasis, pityriasis rosea, lichen planus, lichen striatus, scabies, and fungal infections of the skin.

Eczema is a general term used to describe a type of papulosquamous eruption. The most common eczematous conditions seen in children are atopic dermatitis, seborrheic dermatitis, and contact dermatitis. Atopic dermatitis is a disorder of infancy and childhood and may persist into adulthood. More than half of affected individuals are symptomatic by 1 year of age, and in 90% of cases onset occurs by 5 years of age. The area of involvement changes with age. In infancy, the face, scalp, and extensor surfaces are involved, often areas where the infant can relieve itching by rubbing, and the diaper area is often spared (Figure 138.1A). By childhood, the more typical pattern seen in adults becomes more common: involvement of flexural surfaces such as the neck and antecubital and popliteal fossae. Adults tend to have greater extremity involvement, along with the head and neck. The itching is typically worse at night and can be exacerbated by multiple triggers, including extreme temperatures, sweating, clothing with rough textures, and infections. Clinically, xeroderma (abnormally dry; also called xerosis), erythema, and a pruritic papular eruption are common. Scratching and rubbing lead to crusting and weeping. Eventually, the irritation and inflammation of the skin leads to thickening of the skin, known as lichenification. Changes in color, including hypopigmentation and hyperpigmentation, may also occur. Pityriasis alba, considered to be the mild-est form of atopic dermatitis, presents as hypopigmented areas with fine scale, most commonly observed on the face. Xeroderma is a frequent coexisting condition. Ichthyosis vulgaris, characterized by dirty-appearing excessive scaling and hyperlinear palms, is present in up to one-half of patients affected with atopic dermatitis. Lesions around mucosa (Morgan folds in the infraorbital fold under the eye and cheilitis around the mouth) may also be seen. Symptoms of other atopic conditions, such as allergic rhinitis, asthma, or food-related allergies, may also affect these patients.

Seborrheic dermatitis, which frequently develops during the first 3 months after birth, is characterized by scaly papules or confluent waxy, scaly plaques, particularly of the scalp. Scalp eruptions in infancy are referred to as cradle cap. Seborrheic dermatitis has a pre-dilection for areas with a high density of sebaceous glands, such as the scalp, face, ears, presternal chest, penis, and intertriginous areas, including the folds of the diaper region (Figure 138.1B). The red or pink papules and plaques may have a greasy quality. Secondary infections may occur with Candida, particularly in the intertriginous areas. Seborrheic dermatitis is usually not exceedingly pruritic, in contrast with atopic dermatitis. The intertriginous involvement and the onset shortly after birth may help to differentiate between these 2 dermatitides. Severe seborrheic dermatitis may be associated with an immune deficiency, such as HIV.

Irritant or allergic contact dermatitis occurs when individuals come into physical contact with an irritant or a specific allergen, respectively. Irritant dermatitis is caused by direct cytotoxic effect, while allergic contact dermatitis is a delayed type of hypersensitivity (ie, type IV hypersensitivity reaction) in response to an allergen. Although their etiologies are different, the 2 typically have a similar clinical appearance, with well-defined erythematous vesicles, papules, or plaques, often with scale, oozing, and subsequent lichenification. Diaper dermatitis is among the most common types of irritant dermatitis in the pediatric population (see Chapter 137). Rhus dermatitis (poison ivy/oak), nickel, and fragrance allergy are among the common types of allergic contact dermatitis seen in older children and adolescents. Sensitization to allergens can begin by around 6 months of age. It remains controversial whether atopic dermatitis is a risk factor for allergic contact dermatitis. However, children with atopic dermatitis may have more exposure to sensitizers, in conjunction with a damaged epithelial barrier, putting them at risk.

Figure 138.1. Typical distribution of papulosquamous eruptions in children. A, Atopic dermatitis: usually located on cheeks, creases of elbows, and knees. B, Seborrheic dermatitis: usually located on scalp, behind ears, in thigh creases, and behind eyebrows. C, Scabies: usually located on axillae, webs of fingers and toes, and intragluteal area.

Plaque-type psoriasis, a chronic papulosquamous skin condition manifested most commonly as well-defined erythematous papules and plaques with silvery scale, is not uncommon in childhood. About 40% of adult patients with psoriasis report having had the disease in childhood. It most commonly affects the scalp in the pediatric population as well as the face and intertriginous areas. Infrequently, a young infant may develop psoriasis in the diaper area. Guttate psoriasis features smaller scaly papules and is usually precipitated by group A streptococcal infection in the pharynx or perianal area. Pruritus is variable but not prominent. Classically, psoriatic lesions can develop at sites of trauma (scratches and cuts), known as the Koebner phenomenon. Given that psoriasis is an inflammatory skin condition, clinicians should screen pediatric patients with psoriasis for associated comorbidities, including metabolic and lipid abnormalities, in addition to signs and symptoms of arthritis, depression, and anxiety.

Pityriasis rosea is a self-limited papulosquamous eruption that is frequently seen in adolescents. The lesions tend to be round or ovoid and classically have a symmetric distribution on the trunk extending downward from the midline at a 45° angle, a pattern resembling a pine tree on the back. Classically, there is a larger herald patch preceding the eruption by a few days to weeks. However, the presentation is not always classic; many patients cannot recall a herald patch, and the pattern over the trunk may be haphazard. Pityriasis rosea is generally self-limited and resolves in 1 to 2 months. It is pruritic in about one-quarter of those affected. The etiology is unknown, although some report an association with human herpesvirus 6 or 7 infection.

Lichen planus is an uncommon papulosquamous eruption in the pediatric population, most frequently afflicting children of Arab and Afro-Caribbean backgrounds. It is characterized by pruritic, polygo-nal, pink to purplish flat-topped papules, sometimes with an overlying network of delicate white lines called Wickham striae. Etiology is also unknown, although viruses, including hepatitis C, and medications can occasionally be associated. Flexor surfaces are usually affected, and these lesions can koebnerize. Lichen planus affecting the skin typically resolves within 1 to 2 years; meanwhile, lichen planus involving the mucous membranes and nails, albeit rare in children, may persist.

Lichen striatus is an asymptomatic eruption consisting of flat-topped papules that are skin colored to slightly hyperpigmented. The lesions develop along the Blaschko lines and may be arranged in a curvilinear distribution. This eruption spontaneously resolves over months to years. It is most commonly seen between 9 months and 9 years of age. The etiology is unknown, although up to 85% of individuals with lichen striatus report a personal or family history of atopy.

Scabies may resemble atopic or seborrheic dermatitis in infants and young children. The lesions may be papules, pustules, or vesicles. The characteristic burrow, which is only 3- to 10-mm (0.1- to 0.4-in) long, is often difficult to appreciate unless certain diagnostic maneuvers are undertaken. The lesions are most often noted on the skin of the hands and feet, including the palms and soles in infants and young children. Intertriginous areas, such as the intragluteal region, groin, and finger webs, are commonly infected (Figure 138.1C). In infants and those who are immunocompromised, all skin surfaces, including the face and head, may be involved. Scratching and secondary infection may alter the appearance of the rash. Reddish-brown nodules may be characteristic of more chronic infection. In individuals who are institutionalized or immunosuppressed, extensive mite infection can occur, resulting in thick, greasy-appearing, yellowish scale and crusts over the extremities and trunk, a condition referred to as crusted scabies. The use of long-term topical corticosteroid use has been reported to induce crusted scabies.

Fungal infections (eg, tinea corporis, tinea pedis) commonly appear as papulosquamous eruptions. The lesions usually assume a characteristic morphology, with scaly papules grouped in a circle or coalesced into an annular plaque with central clearing.

Evaluation

History

A thorough history should be obtained (Box 138.2). The presence of a rash in other family members is suggestive of a contagious condition such as scabies or a familial disorder such as atopic dermatitis or psoriasis. An onset in the first few weeks after birth is consistent with seborrheic dermatitis. It is important to determine if any medications have been used because these may modify the appearance of the rash. In addition, certain medications can cause a rash themselves, although these tend to be more morbilliform in appearance (see Chapter 139). Pruritus should be noted. Asking about lesions developing at sites of previous trauma can aid in diagnosing eruptions that koebnerize, such as psoriasis and lichen planus.

Physical Examination

The physical examination helps define the exact nature of the eruption and its distribution, which is often the clue to its etiology. The entire body should be examined, and particular attention should be paid to the intragluteal region and web spaces between fingers and toes. Certain rashes have characteristic appearances. For example, a circular cluster of scaly papules with central clearing signifies tinea corporis, whereas the presence of a herald patch preceding a more generalized eruption can suggest pityriasis rosea. The presence of burrows characterizes scabies. Burrows appear as a 3- to 10-mm (0.1- to 0.4-in) grayish-white line (only about 1 mm [0.04 in] wide). Vesicles, pustules, and nodules may also be present in scabies.

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