Practice Essentials

Psoriasis, which manifests most often as plaque psoriasis, is a chronic, relapsing, inflammatory skin disorder with a strong genetic basis. 

Plaque psoriasis (see the image below) is rarely life threatening, but it often is intractable to treatment.

See Psoriasis: Manifestations, Management Options, and Mimics, a Critical Images slideshow, to help recognize the major psoriasis subtypes and distinguish them from other skin lesions.

Signs and symptoms

Psoriatic plaques are characterized as follows:

  • Raised and easily palpable – Owing to the thickened epidermis, expanded dermal vascular compartment, as well as infiltrate of neutrophils and lymphocytes

  • Irregular to oval in shape

  • One to several centimeters in size

  • Well defined, with sharply demarcated boundaries

  • Very distinctive rich, full red color; lesions on the legs sometimes carry a blue or violaceous tint

  • Typically have a dry, thin, silvery-white or micaceous scale

  • Typically have a high degree of uniformity, with few morphologic differences between the 2 sides

  • Range in number from a few to many at any given time

  • Most often located on the scalp, trunk, and limbs, with a predilection for extensor surfaces, such as the elbows and knees

  • Symmetrically distributed over the body

  • May, in the case of smaller plaques, coalesce into larger lesions, especially on the legs and sacral regions

Other manifestations of plaque psoriasis include the following:

  • Pruritus – One of the main symptoms of plaque psoriasis

  • Nail psoriasis – Nails may exhibit pitting, onycholysis, subungual hyperkeratosis, or the oil-drop sign

  • Inverse psoriasis – A variant of psoriasis that spares the typical extensor surfaces and affects intertriginous areas (ie, axillae, inguinal folds, inframammary creases) with minimal scale

  • Psoriatic arthritis – Occurs in approximately 10-20% of all cases of plaque psoriasis

Manifestations of the psoriatic arthritis include the following:

  • Red, warm, tender, and inflamed joints

  • Joint deformity

  • Dactylitis

  • Sausage digits

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