Psoriasis

6

Psoriasis

Key Points

• Affects up to 2% of the population.

• Chronic disorder in those with a polygenic predisposition combined with triggering factors such as infections (especially streptococcal pharyngitis, but also HIV infection) or medications (e.g. interferon, β-blockers, lithium, or oral CS taper).

• Koebner phenomenon – elicitation of psoriatic lesions by traumatizing the skin.

• Common sites.

– Elbows and knees.

– Nails, hands, feet, trunk (intergluteal fold).

• Skin lesions.

– Most commonly – well-demarcated, erythematous plaques with silvery scale (Fig. 6.1).

Fig. 6.1 Psoriatic plaques. Note the sharp demarcation and silvery scale. Courtesy Julie V. Schaffer, MD.

– Other lesions include sterile pustules, glistening plaques in intertriginous zones.

• Histopathologic findings.

– Regular acanthosis, confluent parakeratosis with neutrophils, hypogranulosis, dilated blood vessels (see Chapter 1).

• Major systemic association is psoriatic arthritis (see Table 6.1), most commonly presenting as asymmetric oligoarthritis of hands/feet; the metabolic syndrome is also common.

Table 6.1

Five types of psoriatic arthritis.

• Pathogenesis.

– Regarded as a T-cell-driven disease involving cytokines, including TNF-α and IL-23 (stimulates Th17 cells).

– Genes that have been associated with psoriasis include those encoding caspase recruitment domain family member 14 (CARD14, a regulator of NF-κB signaling) and, for generalized pustular psoriasis, the IL-36 receptor antagonist (a regulator of IL-8 production and IL-1β responses).

Variants

Chronic Plaque Psoriasis

• Typical lesion – well-demarcated, erythematous plaque with silvery scale.

• Often symmetrical lesions on the elbows and knees; additional sites include the scalp, presacrum, hands, feet, intergluteal fold, and umbilicus (Figs. 6.2–6.4).

Fig. 6.2 Symmetric distribution of psoriatic plaques. Courtesy, Peter C. M. van de Kerkhof, MD.

Fig. 6.3 Palmoplantar psoriasis. Erythematous scaling plaques of the palmar (A) and plantar surfaces (B). Occasionally, there is well-demarcated hyperkeratosis with minimal erythema (C). A, Courtesy, Peter C. M. van de Kerkhof, MD.

Fig. 6.4 Psoriasis of the genitalia. Erythematous plaques with scale on the penis and scrotum. Courtesy, Peter C. M. van de Kerkhof, MD.

• May be generalized (Fig. 6.5).

Fig. 6.5 Widespread chronic plaque psoriasis. Courtesy, Peter CM van de Kerkhof, MD.

• Lesions may be surrounded by a peripheral, blanching ring (Woronoff’s ring), especially when patient is receiving phototherapy.

Guttate Psoriasis

• Typical lesion – small papule or plaque (3 mm to 1.5 cm) with adherent scale (Fig. 6.6).

Fig. 6.6 Guttate psoriasis. A Small discrete papules and plaques of guttate psoriasis in an adolescent; note the Koebner phenomenon. B Numerous papules due to the Koebner phenomenon after a sunburn. B, Courtesy Ronald P. Rapini, MD.

• Generalized distribution.

• Affects children > adults.

• Often preceded by an upper respiratory tract infection.

• In children, may have spontaneous remission but often responds well to UVB phototherapy.

• DDx: pityriasis rosea, syphilis, id reaction to tinea pedis, and small plaque parapsoriasis.

Linear Psoriasis

• Linear, erythematous, scaly lesions that often follow the lines of Blaschko.

• DDx: inflammatory linear verrucous epidermal nevus (ILVEN; follows the lines of Blaschko; resistant to therapy), epidermal nevus with superimposed psoriasis.

Erythrodermic Psoriasis

• Generalized erythema of the skin, with areas of scaling.

• Gradual or acute onset.

• Nail changes, facial sparing, and a history of typical plaque-type psoriasis may be helpful clues.

• May be seen after abrupt tapering of medications, especially CS.

• DDx: other causes of erythroderma, e.g., pityriasis rubra pilaris, generalized atopic dermatitis, Sézary syndrome (see Table 8.2).

Pustular Psoriasis

• Generalized pustular psoriasis (von Zumbusch pattern).

– Erythema and sterile pustules arising within erythematous, painful skin; lakes of pus characteristic (Fig. 6.7).

Fig. 6.7 Pustular psoriasis. Large areas of erythema with numerous pustules. Confluence of pustules creates lakes of pus. Courtesy, Julie V. Schaffer, MD.

– Often associated fever.

– Triggering factors – pregnancy (termed impetigo herpetiformis), rapid tapering of CS, hypocalcemia, infections.

– DDx: acute generalized exanthematous pustulosis (AGEP; pustular drug reaction) (see Chapter 17).

• Palmoplantar (pustulosis).

– Sterile pustules on palms/soles (Fig. 6.8).

Fig. 6.8 Pustulosis of the palms and soles. Multiple sterile pustules are admixed with yellow-brown macules on the palm.

– May have no evidence of psoriasis elsewhere.

– Triggering factors – infections, stress.

Only gold members can continue reading. Log In or Register to continue

Related

Stay updated, free articles. Join our Telegram channel

Tags: Dermatology Essentials E- Book

Apr 22, 2016 | Posted by admin in Dermatology | Comments Off

Full access? Get Clinical Tree

Get Clinical Tree app for offline access

Get Clinical Tree app for offline access