Psoriasis is increasing in both children and adults. The association of comorbidities, specifically obesity and other components of the metabolic syndrome, are also increasing. The precise cause is unknown but genetic and complex immunologic factors play a role in the development of the disease and its comorbidities. There are multiple clinical variants, and the severity of the disease can range from mild localized lesions in most patients to severe generalized involvement in some. Most patients with mild to moderate disease can be controlled with topical treatments.
Key points
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The incidence and prevalence of psoriasis is increasing in the pediatric population.
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There is increasing evidence that childhood psoriasis is associated with the metabolic syndrome.
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Variants of psoriasis in childhood include chronic plaque type, scalp, guttate, inverse, diaper, and nail.
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Topical medications should be used to treat most cases of mild to moderate disease.
Introduction
Overview
Psoriasis is a common chronic scaly inflammatory condition that primarily affects the skin. In this article, what is known about the pathophysiology of the disease, its epidemiology, and overall prognosis are reviewed. The different presentations that can be seen in children as well as clues to clinical diagnosis are discussed. Although thought to primarily be a skin disorder, recent research has linked psoriasis to several comorbidities that are presented below. Finally, skin-directed therapies, which should be helpful in most patients with mild to moderate psoriasis, are discussed.
Pathophysiology
The pathophysiology behind psoriasis is not completely understood. It is thought to be an immune-mediated inflammatory disease of the skin that has a genetic predisposition. Activation of several T cells, Th-1, Th-17, and Th-22, resulting in production of specific cytokines, such as interferon-γ, tumor necrosis factor, IL-17, IL-22, and IL-23, has recently been discovered to play an important role in the development of the disease. These cytokines then activate keratinocytes, leading to increased inflammatory cells and products at the skin site. Epidermal hyperplasia and proliferation of keratinocytes are also a hallmark of psoriasis, which may be due to induction by activated T lymphocytes via inflammatory cytokine response and to an increase in cell cycle turnover.
There is also a known genetic component to psoriasis; those with a first-degree relative with psoriasis have an approximately 5-fold increased risk of developing the disease as compared with the general population, and many children with psoriasis have a first-degree relative with the disease. Furthermore, monozygotic twins have a higher concordance rate than dizygotic twins of developing psoriasis. Several candidate chromosomal regions, termed PSORS1 to PSORS10, have been linked to a risk of developing psoriasis. There is a strong association of the HLA-Cw6 allele with early-onset disease. Several other gene regions, including those encoding some of the implicated interleukins, have also been identified in some affected populations. Although attempts to identify precise etiologic factors continue, it has become apparent that development of the disease results from a complex interplay of both genetic and environmental factors.
Epidemiology
Psoriasis is one of the most common inflammatory skin conditions affecting both children and adults. The worldwide prevalence of psoriasis is estimated at approximately 4%, with ranges from 0% to 8.5% depending on the population studied. In children prevalence is estimated to be as high as 0.71%, with increasing prevalence as age increases to a high of 1.2% at age 18. Incidence of the disease is steadily increasing with a 2-fold increase in both children and adults since 1970. Approximately one-third of patients develop the disease in childhood, with a median age of 10.6 years at first diagnosis. Although psoriasis can develop at any age, cases of congenital psoriasis are extremely rare but up to 27% of children may develop it before age 2. There does not seem to be a gender bias in childhood; when all subtypes of psoriasis are considered, boys and girls develop the disease at equal rates.
Prognosis
Psoriasis is a life-long condition that tends to have a chronic relapsing course. Fortunately, most affected children will have mild disease. Often, mild disease is well-controlled with topical medications requiring intermittent treatment. Some patients with psoriasis are able to achieve complete remission that may last several years. Children are more likely than adults to have the guttate form of psoriasis (described below); those with guttate psoriasis may clear their skin completely without recurrence, develop disease again with streptococcal infection, or go on to develop chronic plaque-type psoriasis. A minority of children with psoriasis unfortunately may worsen with age and may have more severe and widespread involvement, requiring more aggressive treatment.
Introduction
Overview
Psoriasis is a common chronic scaly inflammatory condition that primarily affects the skin. In this article, what is known about the pathophysiology of the disease, its epidemiology, and overall prognosis are reviewed. The different presentations that can be seen in children as well as clues to clinical diagnosis are discussed. Although thought to primarily be a skin disorder, recent research has linked psoriasis to several comorbidities that are presented below. Finally, skin-directed therapies, which should be helpful in most patients with mild to moderate psoriasis, are discussed.
Pathophysiology
The pathophysiology behind psoriasis is not completely understood. It is thought to be an immune-mediated inflammatory disease of the skin that has a genetic predisposition. Activation of several T cells, Th-1, Th-17, and Th-22, resulting in production of specific cytokines, such as interferon-γ, tumor necrosis factor, IL-17, IL-22, and IL-23, has recently been discovered to play an important role in the development of the disease. These cytokines then activate keratinocytes, leading to increased inflammatory cells and products at the skin site. Epidermal hyperplasia and proliferation of keratinocytes are also a hallmark of psoriasis, which may be due to induction by activated T lymphocytes via inflammatory cytokine response and to an increase in cell cycle turnover.
There is also a known genetic component to psoriasis; those with a first-degree relative with psoriasis have an approximately 5-fold increased risk of developing the disease as compared with the general population, and many children with psoriasis have a first-degree relative with the disease. Furthermore, monozygotic twins have a higher concordance rate than dizygotic twins of developing psoriasis. Several candidate chromosomal regions, termed PSORS1 to PSORS10, have been linked to a risk of developing psoriasis. There is a strong association of the HLA-Cw6 allele with early-onset disease. Several other gene regions, including those encoding some of the implicated interleukins, have also been identified in some affected populations. Although attempts to identify precise etiologic factors continue, it has become apparent that development of the disease results from a complex interplay of both genetic and environmental factors.
Epidemiology
Psoriasis is one of the most common inflammatory skin conditions affecting both children and adults. The worldwide prevalence of psoriasis is estimated at approximately 4%, with ranges from 0% to 8.5% depending on the population studied. In children prevalence is estimated to be as high as 0.71%, with increasing prevalence as age increases to a high of 1.2% at age 18. Incidence of the disease is steadily increasing with a 2-fold increase in both children and adults since 1970. Approximately one-third of patients develop the disease in childhood, with a median age of 10.6 years at first diagnosis. Although psoriasis can develop at any age, cases of congenital psoriasis are extremely rare but up to 27% of children may develop it before age 2. There does not seem to be a gender bias in childhood; when all subtypes of psoriasis are considered, boys and girls develop the disease at equal rates.
Prognosis
Psoriasis is a life-long condition that tends to have a chronic relapsing course. Fortunately, most affected children will have mild disease. Often, mild disease is well-controlled with topical medications requiring intermittent treatment. Some patients with psoriasis are able to achieve complete remission that may last several years. Children are more likely than adults to have the guttate form of psoriasis (described below); those with guttate psoriasis may clear their skin completely without recurrence, develop disease again with streptococcal infection, or go on to develop chronic plaque-type psoriasis. A minority of children with psoriasis unfortunately may worsen with age and may have more severe and widespread involvement, requiring more aggressive treatment.
Clinical features
History
The history and presenting symptoms may differ depending on the age of the child and type of psoriasis. Infants with psoriasis most commonly present with a persistent diaper rash that has been refractory to multiple treatments. Older children may present with an asymptomatic scaly rash and/or with refractory or severe dandruff or “cradle cap.” Many children with psoriasis are asymptomatic but many may also present with pruritus and decreased sleep as a result; this is particularly true with psoriasis of the scalp. Patients that present with guttate psoriasis may have had a preceding streptococcal infection of the throat or perianal area.
There are several possible triggers and exacerbating factors of psoriasis in children and include trauma or irritation of the skin, known as the Koebner phenomenon, infection, most commonly streptococcal infection resulting in guttate psoriasis, emotional stress, and medications ( Box 1 ). Although lithium and β-blocker medications are known to trigger psoriasis in adults, these medications are less relevant in childhood psoriasis.
Trauma or local skin irritation (Koebner phenomenon)
Infection
Streptococcal pharyngitis
Perianal streptococcus
Emotional stress
Medications
Antimalarials
Rebound effect after systemic steroids
It has recently been discovered that overweight and obesity are a strong risk factor for the development of childhood in psoriasis. As overweight and obesity are quickly increasing in the pediatric population, this may in part explain the increasing incidence and prevalence of childhood psoriasis.
Physical Examination
The classic psoriatic lesion is a well-demarcated pink-red plaque with overlying silvery-white scale. Removal of this scale by mechanical factors often results in pinpoint bleeding, known as the Auspitz sign. When compared with adults with psoriasis, children tend to have more facial and flexural (especially diaper) involvement and have smaller, thinner plaques, which may lead to some diagnostic confusion. Clinical morphology and symptoms may vary according to the subtype and location on the body of the disease as discussed below and in Table 1 .
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The most common type of psoriasis in both adults and older children is chronic plaque psoriasis ( Fig. 1 ); up to 75% of children with psoriasis have the plaque variant. In this variant of psoriasis, typical well-defined psoriatic lesions are most commonly found on the extensor extremities, but may also be seen on the scalp, trunk, flexures, and face ( Fig. 2 ). Less commonly, plaque psoriasis can have a follicular or annular morphology.
Fig. 1
Chronic plaque psoriasis on the trunk.
Fig. 2
Facial involvement with psoriasis.
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Scalp psoriasis may be seen in isolation or in association with chronic plaque disease. The scalp is often the first site of involvement in children. Scalp lesions are well-defined and scaly and can have varying amounts of underlying erythema ( Fig. 3 ). The occipital scalp and the hairline are common areas of scalp involvement. Scalp scale may be quite thick, also called tinea amiantacea ( Fig. 4 ), and can have associated matting down of the hair, scale surrounding the hair shaft, and resulting nonscarring alopecia. In cases with alopecia, the hair usually returns when disease control is achieved. Scalp psoriasis may be particularly pruritic.
Fig. 3
Scalp psoriasis.
Fig. 4
Tinea amiantacea.
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Guttate psoriasis is the second-most common type of psoriasis seen in children, with a frequency rate of 15% to 30% of all children with psoriasis. This type of psoriasis is characterized by abrupt onset of “droplike” papular lesions of up to 1 cm in size that are symmetrically distributed over the trunk, limbs, and face ( Fig. 5 ). It may be preceded by throat or perianal streptococcal infection. Guttate psoriasis may resolve spontaneously within 3 to 4 weeks, although many patients may go on to develop chronic plaque psoriasis.
Fig. 5
Guttate psoriasis.
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Involvement with psoriasis primarily in the flexural areas and on the face is called inverse psoriasis. This type of psoriasis is more common in children than adults. The morphology of the lesions, particularly in the flexural locations, is often distinct from chronic plaque psoriasis as there can be maceration of the plaques and very little overlying scale due to moisture.
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Diaper or napkin psoriasis is another common variant of psoriasis almost exclusively seen in infancy. Well-defined brightly erythematous plaques that may be macerated are usually seen ( Fig. 6 ). The inguinal folds are usually involved (unlike in irritant contact dermatitis), and erythematous scaly psoriatic lesions may be seen in other locations of the body ( Fig. 7 ). Diaper psoriasis can be particularly difficult to treat and commonly resolves with toilet-training.
Fig. 6
Diaper psoriasis.
Fig. 7
Diaper psoriasis with typical psoriatic papules and plaques elsewhere.
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Nail psoriasis is less common in children than in adults but can be seen in up to 40% of children with psoriasis. Nail changes that may be seen are pitting, overall roughness (trachyonychia), onycholysis (distal separation of the nail plate from the nail bed), oil spots, and subungual hyperkeratosis ( Fig. 8 ). These changes can be seen in isolation, can precede, coincide with, or come after the onset of skin psoriasis. Nail involvement of psoriasis is very difficult to treat.
Fig. 8
Nail psoriasis with pitting, oil spots, and onycholysis.
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Pustular psoriasis is a rare variant whereby sterile superficial pustules are seen in localized or generalized fashion ( Fig. 9 ). Those with generalized pustular psoriasis may be systemically ill with fever and malaise. Although pustular psoriasis is more common in adults, an annular configuration of pustules is seen more commonly in children than adults. The pustular variant of psoriasis is often mistaken for infection.
Fig. 9
Pustules with underlying erythema in pustular psoriasis.
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Erythrodermic psoriasis is another rare variant characterized by greater than 90% body surface area involvement with erythema. Scaling may be minimal. This type of psoriasis is extremely rare.
| Type | Age Group | Clinical Findings | Differential Diagnosis |
|---|---|---|---|
| Chronic plaque | Any age | Well-defined erythematous plaques, silvery white scale Auspitz sign Extensor surfaces, trunk, periumbilical May be follicular or annular | Nummular eczema Atopic dermatitis Tinea corporis Pityriasis rubra pilaris |
| Scalp | Any age | Well-defined erythematous scaly plaques Tinea amiantacea Often extends onto forehead | Seborrheic dermatitis Tinea capitis Atopic dermatitis |
| Guttate | Children, adolescents, young adults | Small, “drop-like” <1 cm erythematous scaly papules Trunk, extremities, face, scalp | Pityriasis rosea Tinea corporis Pityriasis rubra pilaris Nummular eczema |
| Inverse | Younger children | Erythematous plaques with little scale, possible maceration Flexural areas and face | Intertrigo Seborrheic dermatitis Erythrasma Contact dermatitis |
| Diaper/napkin | Ages 0–2 | Well-defined bright red plaques in diaper area Little scale, may be macerated Involves inguinal folds | Irritant contact dermatitis Allergic contact dermatitis Intertrigo Candidal diaper dermatitis Acrodermatitis enteropathica |
| Nail | Any age, more common in older children and adults | Pitting, onycholysis, oil spots, subungual hyperkeratosis, trachyonychia May or may not have skin signs of psoriasis | Onychomycosis Pityriasis rubra pilaris Lichen planus |
| Pustular | Older children and adults | Superficial sterile pustules on erythematous skin May have annular configuration May be localized to palmoplantar areas | Candida infection Dyshidrotic eczema Staphylococcal scalded skin syndrome Blistering dactylitis Tinea infection |
| Erythrodermic | Any age | Generalized erythema Minimal scale Very rare | Staphylococcal scalded skin syndrome Pityriasis rubra pilaris Cutaneous T-cell lymphoma Atopic dermatitis |
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