EPIDEMIOLOGY

AGE 10% have onset of lesions before age 10, and up to 33% have onset by age 20 years.

GENDER Slight predominance F > M.

PREVALENCE 2% of the world’s population. United States and Canada: 4% to 5% of the population.

RACE Low incidence in Asians, Africans, African Americans, American Indians, and Japanese relative to Caucasians.

OTHER FEATURES Multifactorial inheritance. Minor trauma is a predisposing factor (45% of patients) in eliciting lesions (Koebner’s phenomenon). Infection (particularly streptococcal) also plays a role. Many episodes of psoriasis—and particularly guttate psoriasis— follow sore throats or upper respiratory infections. Stress, cold weather, hypocalcemia, and lack of sunlight exposure aggravate the condition. Certain drugs (lithium, interferon, β-blockers, alcohol, antimalarials, corticosteroid withdrawal, and paradoxically anti-TNFα biologics) can also precipitate psoriasis.

PATHOPHYSIOLOGY

Psoriasis is likely a polygenic disease caused by the inappropriate activation of T cells (the adaptive immune system) as well as abnormal keratinocyte proliferation (the innate immune system). A predominantly T_H1 inflammatory milieu underlies the chronic inflammation of psoriasis. Several cytokines including interferon-α, TNF-α, interleukin 23, and interleukin 17 are known to play critical roles in the initiation and prolongation of the inflammation in psoriasis that drives T-cell recruitment and increased keratinocyte proliferation.

HISTORY

ONSET OF LESIONS Usually slowly over the course of months but may be sudden as in acute guttate psoriasis and generalized pustular psoriasis (von Zumbusch).

SKIN SYMPTOMS Pruritus is reasonably common, especially in scalp and anogenital psoriasis.

CONSTITUTIONAL SYMPTOMS In 5% of cases, psoriasis can be associated with arthritis, fever, and/or an “acute illness” syndrome (weakness, chills, fever) with generalized erythroderma.

PHYSICAL EXAMINATION

Skin Findings

TYPE Well-delineated, erythematous, thickened plaques with a characteristic silvery-white scale (Fig. 4-1A). Removal of scale results in the appearance of miniscule blood droplets (Auspitz sign).

COLOR Salmon pink to red.

SIZE Can range from pinpoint 1-mm papules to large 20- to 30-cm plaques.

SHAPE Round, oval, polycyclic, or annular. Lesions may take on sharply geometric shapes when arising in sites of trauma or repeated pressure (Koebner’s phenomenon).

DISTRIBUTION Localized (e.g., elbows), regional (e.g., scalp), generalized (e.g., guttate psoriasis or erythroderma). Often symmetrically distributed over the body.

SITES OF PREDILECTION Favors elbows (Fig. 4-1B), knees, facial region, scalp, and intertriginous areas (axillae, inguinal folds, intergluteal cleft).

OTHER Scalp involvement is common (Fig. 4-1C), with predilection for the occiput. Hair loss (alopecia) is not a common feature even with severe scalp involvement. Fingernails and toenails are sometimes involved. Nail changes include pitting, subungual hyperkeratosis, onycholysis, and yellow spots under the nail plate “oil spot” (Fig. 4-1D).

General Findings

Psoriatic arthritis is rare before age 40 and occurs in 5% to 30% of the patients with skin findings. Arthritis may be mono- and symmetric oligoarthritis of the DIPs and PIPs, arthritis exclusively of the DIPs, rheumatoid arthritis-like in medium-sized joints (PIP, MCP, wrists, ankles, and elbows), arthritis mutilans with severe joint destruction or spondylitis, and sacroiliitis. Children with psoriasis are more likely to be obese.

DIFFERENTIAL DIAGNOSIS

Psoriasis may be confused with seborrheic dermatitis. The two entities may be indistinguishable and often an overlap, so-called sebopsoriasis presentation can be seen. Psoriasis must also be distinguished from atopic dermatitis, lichen simplex chronicus, pityriasis rosea, tinea corporis, contact dermatitis, psoriasiform drug eruptions (such as from β-blockers, gold, and methyldopa), and cutaneous T-cell lymphoma.

LABORATORY EXAMINATIONS

DERMATOPATHOLOGY Skin biopsy reveals (1) epidermal hyperplasia with thinning of the suprapapillary plates and elongation of the rete ridges; (2) increased mitosis of keratinocytes, fibroblasts, and endothelial cells; (3) parakeratotic hyperkeratosis (nuclei retained in the stratum corneum); and (4) inflammatory cells in the dermis (usually lymphocytes and monocytes) and in the epidermis (polymorphonuclear cells), forming microabscesses of Munro in the stratum corneum.

THROAT CULTURE Throat culture for β-hemolytic streptococcus is indicated in cases of guttate psoriasis or in cases that are precipitated by a sore throat. If positive, antibiotic may be needed to clear the infection, which in some cases may speed resolution of the psoriasis.

COURSE AND PROGNOSIS

Psoriasis typically has a chronic course with numerous remissions and exacerbations. Some children progress to mild disease with intermittent asymptomatic flares. Other children have a more severe course with recurrent extensive flares, and 5% may develop an associated arthritis in adulthood.

MANAGEMENT

The treatment of psoriasis depends upon the extent and severity of the disease, as well as the site involved. While not usually as itchy as atopic dermatitis, many patients complain of pruritus. Patients should be instructed never to rub or scratch the areas since trauma can precipitate psoriatic plaques (Koebner’s phenomenon).

1. Emollients such as petrolatum, mineral oil, Vaseline, or moisturizers (CeraVe, Eucerin, Moisturel, and Aquaphor creams) should be used to keep the skin well hydrated.

2. Judicious ambient sunlight exposure helps psoriasis, and children should be encouraged to cautiously expose the affected areas to the sun for short periods of 15 to 20 minutes during the day. Sunscreen should be used, and sunburning should be avoided.

3. Baths are helpful in soothing the pruritus and removing the scale. They should be lukewarm and limited to 10 minutes in duration. For some, it may be helpful to add bath oil, salt, or tar (Balnetar bath oil) to the water to soften scale and soothe dry skin.

4. Tar preparations can be suggested to reduce the skin inflammation. Bath emulsions, creams (Elta tar), and ointments (MG217) can be used twice daily, but are not recommended for prolonged periods of time.

5. Topical steroid creams are effective if used in appropriate strengths:

   1. Low-potency steroids (desonide 0.05%, 1% or 2.5% hydrocortisone) can be used on the face and groin area, no more than bid × 2 weeks per month.

   2. Medium-potency steroids (mometasone 0.1%, fluticasone 0.05%, triamcinolone 0.1%) can be used on the extremities or body no more than bid × 2 weeks per month.

   3. High-potency steroids (clobetasol 0.05%, diflorasone 0.05%, betamethasone dipropionate 0.05%) should be reserved for older children/adults on severely affected areas bid for no more than 2 weeks.

6. Oral antibiotics may be effective, especially in guttate psoriasis flares precipitated by Streptococcus pharyngitis. Certain antibiotics also possess anti-inflammatory properties and can help if there are signs of secondary infection—open moist areas that weep or become crusted. Some commonly prescribed antibiotics include penicillin VK (25–50 mg/kg/d divided qid, not to exceed 3 g/d), cephalexin (25–50 mg/kg/d divided qid, not to exceed 4 g/d), dicloxacillin (25–50 mg/kg/d divided qid, not to exceed 2 g/d), and erythromycin (30–50 mg/kg/d divided qid, not to exceed 2 g/d).

7. Steroid-sparing topical creams include the following:

   1. Vitamin D analogs (calcipotriene 0.005%) typically used bid to affected areas. Calcipotriene may also be used in conjunction with topical steroids. A commonly used maintenance schedule recommends calcipotriene applied bid to affected areas Monday through Friday and a topical steroid applied bid Saturday and Sunday.

   2. Retinoids (tazarotene 0.1% cream or gel) can be used to decrease epidermal proliferation and is applied qhs to affected areas. The retinoids typically help reduce the psoriatic scale, but often are too irritating for use in younger children.

   3. Anthralins (Drithocreme, Dritho-Scalp) have an antiproliferative effect and can be used qid to affected areas, but often are too irritating for use in younger children.

8. For the scalp, tar (T/Gel, DHS) selenium sulfide (Selsun), zinc pyrithione (Head & Shoulders), salicylic acid (T/Sal), or ketoconazole (Nizoral) shampoos used two or three times per week can help reduce scaling. Topical steroid solutions (fluocinolone 0.01% scalp solution) can be applied qam sparingly to the affected areas to help decrease erythema and itching.

9. Phototherapy with UVB, narrow band UVB, or PUVA (psoralen with UVA) works well, but increases the lifetime risk of skin cancer, and is usually not recommended for children.

10. Systemic agents including methotrexate, cyclosporine, systemic retinoids (acitretin), and systemic biologic agents (etanercept, infliximab, adalimumab, ustekinumab) are reserved for severe, refractory cases or those with significant associated arthritis and warrant careful prescreening and close blood monitoring.

PSORIASIS VULGARIS, GUTTATE TYPE

PHYSICAL EXAMINATION

Skin Lesions

TYPE Papules 2 mm to 1 cm.

COLOR Salmon pink.

SHAPE Guttate, “spots that resemble drops” (Fig. 4-2).

ARRANGEMENT Scattered discrete lesions.

DISTRIBUTION Generalized, usually sparing the palms and soles and concentrating on the trunk, less on the face, scalp, and nails.

DIFFERENTIAL DIAGNOSIS

Guttate psoriasis needs to be differentiated from pityriasis rosea, viral exanthem, psoriasiform drug eruption, and secondary syphilis.

LABORATORY EXAMINATION

SEROLOGIC An increased antistreptolysin O, anti-DNase B, or streptozyme titer in those patients with antecedent streptococcal infection.

THROAT CULTURE May be positive for β-hemolytic Streptococcus pyogenes (Group A β-hemolytic streptococcus).

COURSE AND PROGNOSIS

Often, but not always, this type of psoriasis spontaneously disappears in a few weeks. Resolution may be expedited in some individuals with antibiotic treatment.

MANAGEMENT

The resolution of lesions can be accelerated by judicious exposure to sunlight. For persistent lesions, treatment is same as for generalized plaque psoriasis. Penicillin VK (25–50 mg/kg/d divided qid, not to exceed 3 g/d) if group A β-hemolytic Streptococcus is cultured from throat.

PALMOPLANTAR PUSTULOSIS

PHYSICAL EXAMINATION

Skin Lesions

TYPE Pustules that evolve into crusts and scaling.

COLOR Dusky red base, yellow pustules.

SIZE 2 to 5 mm.

DISTRIBUTION Localized to palms (Fig. 4-3A) and soles (Fig. 4-3B).

DIFFERENTIAL DIAGNOSIS

Palmoplantar pustulosis needs to be differentiated from tinea manuum, tinea pedis, dyshidrotic eczema, and contact dermatitis.

LABORATORY EXAMINATION

DERMATOPATHOLOGY Skin biopsy reveals edema and exocytosis of mononuclear cells forming a vesicle. Later, neutrophils form a pustule.

COURSE AND PROGNOSIS

Palmoplantar pustulosis can recur for years and is difficult to treat. Infrequently, psoriasis vulgaris may develop elsewhere. Pustulosis of the palms and soles can very rarely be associated with sterile inflammatory bone lesions (chronic recurrent multifocal osteomyelitis, pustulotic arthroosteitis, and SAPHO syndrome: synovitis, acne, pustulosis, hyperostosis, and osteitis). Some hereditary cases have been associated with a mutation in the IL36RN gene encoding the interleukin-36 receptor antagonist protein.

MANAGEMENT

The resolution of lesions can be accelerated by judicious exposure to sunlight. Steroids under occlusion at night can hasten resolution. Systemic treatments such as methotrexate, cyclosporine, retinoids, or biologic agents are often necessary to achieve disease control.

PSORIASIS VULGARIS, ERYTHRODERMIC

SYNONYMS Dermatitis exfoliativa, erythroderma of Wilson–Brocq.

EPIDEMIOLOGY

AGE Any age.

GENDER M > F.

INCIDENCE Rare.

ETIOLOGY In childhood, erythroderma is more likely owing to pre-existing dermatitis such as atopic dermatitis or psoriasis.

CLASSIFICATION Acute phase with generalized scaly erythema and fever, lymphadenopathy. Chronic form characterized by nail dystrophy but no loss of scalp and body hair (compared to other forms of erythroderma, e.g., drugs, mycosis fungoides).

HISTORY

DURATION OF LESIONS Acute onset of systemic symptoms and red swollen patches and plaques that evolve into a widespread exfoliative erythema in the setting of previous psoriasis.

SKIN SYMPTOMS Generalized pruritus.

GENERALIZED SYMPTOMS Chills, malaise, fatigue, anorexia, weight loss.

PHYSICAL EXAMINATION

Skin Findings

TYPE OF LESIONS Confluent diffuse erythema covered by laminated scales. Skin becomes dull, scarlet, swollen, with areas of oozing (Fig. 4-4). Desquamation usually occurs after a few days. The palms and soles are covered by thick scales and have deep fissures. Secondary infections by bacteria can develop.

COLOR Bright red.

ARRANGEMENT Confluent.

DISTRIBUTION Generalized.

HAIR Normal.

NAILS Onycholysis, shedding of nails with dystrophy.

General Findings

Generalized lymphadenopathy.

DIAGNOSIS AND DIFFERENTIAL DIAGNOSIS

DIAGNOSIS Clinical diagnosis of psoriatic erythroderma is not always easy, especially in the absence of previous history of psoriasis. Cutaneous signs of psoriasis are helpful, such as pitting of the nails, psoriasiform plaques on the scalp, or intergluteal erythema.

DIFFERENTIAL DIAGNOSIS Other causes of erythroderma include pityriasis rubra pilaris (PRP), seborrheic dermatitis (erythroderma desquamativa), drug hypersensitivity, atopic dermatitis, cutaneous T-cell lymphoma, lichen planus, pemphigus foliaceous, epidermolytic hyperkeratosis (EHK), and acute graft-versus-host disease.

LABORATORY EXAMINATIONS

HEMATOLOGY Elevated sedimentation rate.

CHEMISTRY Low serum albumin and increased γ-globulins. Young children may be especially prone to dehydration from increased insensible transepidermal water losses and present with hypernatremia. Hypocalcemia may also be seen in erythrodermic states.

MICROBIOLOGY Blood cultures will be negative (usually obtained to rule out infection in the setting of high fever).

DERMATOPATHOLOGY Psoriasiform dermatitis with elongated and thickened ridges, marked parakeratosis, absent granular layer, intra- and intercellular edema, epidermal invasion by leukocytes, and a dermal perivascular inflammatory infiltrate.

COURSE AND PROGNOSIS

Variable. Can be very prolonged and recurrent.

MANAGEMENT

Supportive care often requiring hospitalization is necessary to maintain fluid–electrolyte homeostasis and body temperature. Skin biopsy should be performed if the cause of the erythroderma is not known (no known predisposition to psoriasis). Topical treatments include emollients and steroids under occlusive wraps. Systemic steroids, retinoids, or immunosuppressives (methotrexate or cyclosporin) may be necessary. In older children, phototherapy with UVB, narrow band UVB, or PUVA may be helpful.

SYNONYM Tinea amiantacea.

EPIDEMIOLOGY

AGE Typically school age children and adolescents.

GENDER F > M.

INCIDENCE Uncommon.

ETIOLOGY Often a manifestation of other underlying skin disease with scalp involvement such as psoriasis, seborrheic dermatitis, or atopic dermatitis.

RACE All races.

HISTORY

DURATION OF LESIONS Individuals present with chronic scalp flaking associated with bound-down areas of thick, adherent scales. The shiny appearance of the heaped-up scales gives rise to the name “amiantacea,” resembling the appearance of asbestos.

SKIN SYMPTOMS Associated symptoms may include pruritus, tingling, or burning of the scalp. The chronicity of the lesions may be associated with patchy or diffuse alopecia.

PHYSICAL EXAMINATION

TYPE Erythematous plaques with adherent, thick yellowish scale (Fig. 4-5).

COLOR Yellow to white or gray.

ARRANGEMENT Individual plaques or confluent, diffuse involvement.

DISTRIBUTION May be localized or present throughout the scalp and the scale may be adherent to the hair.

GENERAL FINDINGS May be associated with other signs of underlying skin disease (e.g., plaques of psoriasis on the body).

DIFFERENTIAL DIAGNOSIS

Pityriasis amiantacea is generally thought to be a subset of scalp psoriasis or seborrheic dermatitis; it needs to be differentiated from tinea capitis. No pathogenic organisms are present in pityriasis amiantacea.

COURSE AND PROGNOSIS

Pityriasis amiantacea is chronic, remitting, and difficult to treat.

MANAGEMENT