A 5-year-old boy presents to his pediatrician with a new onset rash 2 weeks after being treated for strep pharyngitis. He had been treated with a10-day course of amoxicillin after a positive rapid strep test in the office. The mother states that her son is otherwise feeling well with a good appetite and no change in his activities. The pediatrician notes small plaques on the child’s face, arms and trunk and sees the resemblance to drops of water (Figure 136-1). The vital signs are normal as is the rest of the physical examination. A diagnosis of guttate psoriasis is made without any laboratory tests or biopsies. The child is started on 0.1 percent triamcinolone ointment to be applied twice daily. A referral to dermatology is also made.
Psoriasis is a chronic inflammatory papulosquamous and immune-mediated skin disorder. It is also associated with joint and cardiovascular comorbidities. Psoriasis can present in many different patterns, from the scalp to the feet, and cause psychiatric distress and physical disabilities. It is crucial to be able to identify psoriasis in all its myriad presentations so that patients receive the best possible treatments to improve their quality of life and avoid comorbidities.
Psoriasis affects approximately 2 percent of the world population.1
The prevalence of psoriasis was 2.5 percent in white patients and was 1.3 percent in African American patients in one population study in the US.2
Sex—No gender preference.
Age—Psoriasis can begin at any age. In one population study of the age of onset of psoriasis two peaks was revealed, one occurring at the age of 16 years (female) or 22 years (males) and a second peak at the age of 60 years (female) or 57 years (males).3
The prevalence rates for pediatric psoriasis increased in a linear way from 0.2 percent at the age of one year to 1.2 percent at the age of 18 years in a German study.4
Psoriasis begins before the age of 20 in about 1/3 of patients.5
Psoriatic arthritis affects about 20 percent of all psoriasis patients.5
Immune-mediated skin disease, where the T cell plays a pivotal role in the pathogenesis of the disease.
Langerhans cell (antigen-presenting cells in the skin) migrate from the skin to regional lymph nodes, where they activate T cells that migrate to the skin and release cytokines.
Cytokines are responsible for epidermal and vascular hyperproliferation and proinflammatory effects.
Family history.
Obesity.
Smoking and environmental smoke.
Heavy alcohol use.
Table 136-1 lists the factors that trigger and exacerbate psoriasis.6
The risk of psoriasis is higher with:7
Family history of psoriasis (odds ratio [OR] = 33.96; 95 percent confidence interval [CI] 14.14 to 81.57).
Urban dwellers (OR = 3.61; 95% CI = 0.99 to 13.18).
Alcohol consumption (OR = 2.55; 95% CI = 1.26 to 5.17).
Environmental tobacco smoke at home (OR = 2.29; 95% CI = 1.12 to 4.67).
In a multicenter case-control study of environmental risk factors in pediatric psoriasis the most important risk factors were:
Environmental tobacco smoke at home or smoking—Odds ratio 2.90 (95% confidence interval [CI] = 2.27–3.78).
Stressful life events—Odds ratio 2.94 (95% CI = 2.28–3.79).
Higher BMI (>26)—odds ratio 2.52 (95% CI = 1.42–4.49).8
Psoriasis has many forms and locations. These nine categories were used to describe psoriasis in a consensus statement of the American Academy of Dermatology (AAD):9
Plaque psoriasis (Figure 136-2).
Scalp psoriasis (Figure 136-3).
Guttate psoriasis (Figures 136-4 and 136-5).
Inverse psoriasis (Figure 136-6).
Palmar-plantar psoriasis (Figure 136-7); also known as palmoplantar psoriasis.
Erythrodermic psoriasis (Figure 136-8).
Pustular psoriasis—Localized and generalized (Figure 136-9).
Nail psoriasis (Figure 136-10; see Chapter 165, Psoriatic Nails).
Psoriatic arthritis (Figure 136-11).
FIGURE 136-9
Pustular psoriasis in a 3-year-old boy. He presented with fever, erythroderma and no history of psoriasis. He was admitted for a presumed infection and then developed pustules. He was started on cyclosporine as an inpatient and then transitioned to acitretin as an outpatient. Note the clusters of pustules and the exfoliation of skin at the borders of the involved areas. A. Many pustules are visible on the lower leg. B. Pustules on the other leg are on the edge of an area of erythema. (Used with permission from Emily Becker, MD.)
FIGURE 136-10
Nail pitting from psoriasis in a 3-year-old girl. This is the same girl with plantar psoriasis in Figure 136-7. (Used with permission from Richard P. Usatine, MD.)
Typical distribution involves: elbows, knees, extremities, trunk, scalp, face, ears, hands, feet, genitalia, and intertriginous areas, and nails.
White scale on an erythematous raised base with well-demarcated borders (Figures 136-2).
Plaques can appear in different colors including silvery gray (Figure 136-12) and hypopigmented (Figure 136-13).
Positive Auspitz sign in which the peeling of the scale produces pinpoint bleeding on the plaque below.
Typical distribution includes the elbows and knees and other extensor surfaces. The plaques can be found from head to toe including the umbilicus, vulva, and penis. In children, plaques are more likely to be seen on the face than in adults (Figure 136-14).
Plaques tend to be symmetrically distributed.
Plaques can be annular with central clearing (Figure 136-15).
When plaques occur at a site of injury, it is known as the Koebner phenomenon.
Plaque on the scalp that may be seen at the hairline and around the ears (Figure 136-3).
The thickness and extent of the plaques are variable as seen in plaque psoriasis.
Small round plaques that resemble water drops (guttate means like a water drop; Figure 136-16).
Classically described as occurring after strep pharyngitis or another bacterial infection. This is one type of psoriasis that occurs in childhood.
Typical distribution—The trunk and extremities but may include the face and neck (Figures 136-1 and 136-5).
Found in the intertriginous areas of the axilla, groin, inframammary folds, and intergluteal fold (Figure 136-6). It can also be seen within adipose folds in obese individuals.
The term inverse refers to the fact that the distribution is not on extensor surfaces but in areas of body folds.
Morphologically the lesions have little to no visible scale.
Color is generally pink to red but can be hyperpigmented in dark-skinned individuals.
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