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Psoriasis is a common chronic inflammatory disease of the skin. They are symmetric in distribution and favor elbows, knees, scalp, retroauricular skin, and intertriginous areas. Many clinical variants exist and include plaque psoriasis, pustular psoriasis, guttate psoriasis, inverse psoriasis, and erythrodermic psoriasis, with the plaque variant being the most common type (Figs. 56.1 and 56.2). Nails and mucous membranes can be affected. Psoriasis is associated with psoriatic arthritis in at least 5% of patients.

Figure 56.1

Classic psoriatic plaques on the knees

Figure 56.2

Psoriatic plaques koebnerizing vitiligo patches


Incidence: About 1.5% to 2% of the world’s population

Age: can occur at any age. Two peaks of onset, the second and sixth decades. Onset is earlier in women. Uncommonly affects children

Race: lower incidence in African Americans, Native Americans, and Asians

Sex: equal

Precipitating factors: bacterial infections, especially streptococcal infection (guttate psoriasis), trauma (Koebner phenomenon), stress, genetic predisposition, and medication use (most commonly lithium, beta blockers, antimalarials). Rapid corticosteroid tapers may induce pustular psoriasis


Polygenic disease with a 41% risk for a child to develop psoriasis if both the parents are affected. The primary pathophysiology involves hyperproliferation and abnormal differentiation of epidermal keratinocytes as well as abnormal cellular immune response.


Plaque variant with well-demarcated, pink to erythematous papules and plaques with overlying silvery-white scale. Pinpoint bleeding observed with scale removal (Auspitz sign). Guttate variant with tear drop-shaped lesions. Erythematous generalized pustules are seen with pustular psoriasis.


Tinea corporis, seborrheic dermatitis, eczematous dermatitis, mycosis fungoides, parapsoriasis, lichen simplex chronicus, pityriasis rubra pilaris, Reiter’s disease, Bowen’s disease.



Antistreptolysin O(ASO) titer for guttate psoriasis.


Regular psoriasiform epidermal hyperplasia with absent granular cell layer and thinning above the dermal papillae. Other characteristic features include collections of neutrophils in epidermis as well as tortuous blood vessels in the papillary dermis.


This disease demonstrates a chronic course with multiple exacerbations and remissions, which can be seasonal or related to stress.


There are multiple therapeutic options for treatment of psoriasis. Choosing an appropriate therapy depends on the age, health, and preferences of the patient. It also depends on the extent of the psoriasis. The costs of therapy vary dramatically as well. Alternative therapies are most appropriate in refractory cases. Assessing the side-effect profile of treatments is another ...

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