Psoriasis is a hereditary disorder of skin characterized by chronic
scaling papules and plaques in a characteristic distribution, largely
at sites of repeated minor trauma. The HLA types most frequently
associated with psoriasis are HLA-B13, -B17, -Bw16, -B37, -Cw6,
It can be difficult to distinguish between atopic dermatitis
and psoriasis in infancy. If family history and cutaneous findings
are not helpful, one hint is atopic dermatitis usually spares the
diaper area and psoriasis favors that location.
Age 10% have onset of
lesions before age 10, and 37% have onset before age 20.
Prevalence 2% of the world’s
population. United States and Canada: 4% to 5% of
Race Low incidence in Asians, Africans,
African Americans, American Indians, and Japanese.
Other Features Multifactorial inheritance.
Minor trauma is a major factor (45% of patients) in eliciting
lesions (Koebner’s phenomenon). Infection (particularly
streptococcal) also plays a role. Many episodes of 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) can also precipitate psoriasis.
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).
Onset of Lesions Usually, 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.
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
Psoriasis vulgaris A. Well-delineated
erythematous plaques with a silvery-white scale characteristic of
psoriasis. B. Well-delineated erythematous
plaque located on the elbow of a child with psoriasis. Psoriasis vulgaris, scalp, and nail findings.
C. Diffuse erythema and scale in the scalp of a child with
psoriasis. Hair loss is minimal. D. Pinpoint
pits, distal onycholysis, and yellowish discoloration (so-called
oil-spot) seen in the fingernails of a child with psoriasis.
Color Salmon pink to red.
Size Can range from pinpoint 1-mm
papules to large 20- to 30-cm plaques.
Shape Round, oval, polycyclic,
Distribution Localized (e.g., elbows),
regional (e.g., scalp), generalized (e.g., guttate psoriasis or
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). 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.
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 DIPs, rheumatoid arthritislike in medium-sized joints
(PIP, MCP, wrists, ankles, and elbows), arthritis mutilans with
severe joint destruction or spondylitis, and sacroiliitis.
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
(from β-blockers, gold, and methyldopa), and cutaneous T-cell lymphoma.
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
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 both the infection and the psoriasis.
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.
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. Ambient sunlight exposure helps psoriasis, and children should
be encouraged to cautiously expose the affected areas to the sun
for short periods 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.
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
5. Topical steroid creams are effective if used in appropriate
- a. 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 wks/mo.
- b. Medium-potency steroids (mometsaone 0.1%, fluticasone
0.05%, triamcinolone 0.1%) can be used on the
extremities or body no more than bid × 2 wks/mo.
- c. 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 (see Topical Corticosteroids).
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),
cefadroxil (30 mg/kg/d divided bid), and erythromycin
(30–50 mg/kg/d divided qid, not to exceed
7. Steroid-sparing topical creams include the following:
- a. Vitamin D analogs (calcipotriene 0.005%) typically
used bid to affected areas. It 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.
- b. 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.
- c. Anthralins (Drithrocreme, 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), 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. Methotrexate, cyclosporin, systemic retinoids (acitretin),
and systemic biologic agents (alefacept, efalizumab, etanercept,
infliximab, adalimumab) are typically not used in children and reserved
for severe, refractory cases with careful prescreening and close
Guttate psoriasis is an acute flare of multiple generalized small
psoriatic plaques that often follows streptococcal pharyngitis.
This form is relatively rare (2% of all psoriasis cases),
but commonly seen in children and often clears. Guttate psoriasis
may be more chronic, especially in adults, and may be unrelated
to streptococcal infection.
Type Papules 2 mm to 1 cm.
Shape Guttate (Latin, “spots
that resemble drops”).
Arrangement Scattered discrete
lesions (Fig. 4-2).
Psoriasis vulgaris, guttate
type Erythematous scaling papules on the trunk of an adolescent
after streptococcal pharyngitis.
Distribution Generalized, usually
sparing the palms and soles and concentrating on the trunk, less
on the face, scalp, and nails.
Guttate psoriasis needs to be differentiated from pityriasis
rosea, viral exanthem, psoriasiform drug eruption, and secondary
Serologic An increased antistreptolysin
O, anti-DNase B, or streptozyme titer in those patients with antecedent
Throat Culture May be positive
for β-hemolytic Streptococcus aureus.
Often, but not always, this type of psoriasis spontaneously disappears
in a few weeks, especially with antibiotic treatment.
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 is a rare, relapsing eruption limited
to the palms and the soles characterized by numerous sterile yellow,
deep-seated pustules that evolve into crusts and scales.
Type Pustules that evolve into
crusts and scaling.
Color Dusky red base, yellow pustules.
Distribution Localized to palms
(Fig. 4-3A) and soles (Fig. 4-3B).
Palmoplantar pustulosis, palms,
and soles A. Deep-seated yellow vesicles on the palms which
progress to crusts and scales. B. The
soles of the same individual with similar deep-seated pustular lesions.
Palmoplantar pustulosis needs to be differentiated from tinea
manuum, tinea pedis, dyshydrotic eczema, and contact dermatitis.
Dermatopathology Skin biopsy reveals
edema and exocytosis of mononuclear cells forming a vesicle. Later,
neutrophils form a pustule.
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).
The resolution of lesions can be accelerated by judicious exposure
to sunlight. Steroids under occlusion at night can hasten resolution.
Erythrodermic psoriasis is a serious, often life-threatening
condition in patients with psoriasis, characterized by full-body
redness (erythroderma) and scaling. A preexisting dermatosis can
be identified in 50% of patients and psoriasis is the second
most common cause of erythroderma after atopic dermatitis.
Erythroderma is one of the true dermatologic emergencies. An
etiology should be sought quickly and supportive care initiated
Synonyms Dermatitis exfoliativa,
erythroderma of Wilson–Brocq.
Etiology In childhood, erythroderma
is more likely owing to preexisting dermatitis such as atopic dermatitis
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).
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
Skin Symptoms Generalized pruritus.
Generalized Symptoms Chills, malaise,
fatigue, anorexia, weight loss.
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.
Psoriasis vulgaris: erythrodermic Entire
skin surface is dull-red with diffuse swelling and oozing.
Nails Onycholysis, shedding of
nails with dystrophy.
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, seborrheic dermatitis,
drug hypersensitivity, atopic dermatitis, cutaneous T-cell lymphoma,
lichen planus, pemphigus foliaceous, epidermolytic hyperkeratosis,
and acute graft-versus-host disease.
Hematology Elevated sedimentation
Chemistry Low serum albumin and
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.
Variable. Can be very prolonged and recurrent.
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 treatment
includes emollients and steroids under 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.