Practice Essentials
Psoriasis, which manifests most often as plaque psoriasis, is a chronic, relapsing, inflammatory skin disorder with a strong genetic basis. Plaque psoriasis is rarely life threatening, but it often is intractable to treatment.
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
Diagnosis
Histology
Histologic epidermal findings include the following:
• Mitotic activity of basal keratinocytes is increased almost 50-fold, with keratinocytes migrating from the basal to the cornified layers in only 3-5 days rather than the normal 28-30 days
• The epidermis becomes thickened or acanthotic in appearance, and the rete ridges increase in size
• Abnormal keratinocyte differentiation is noted throughout the psoriatic plaques, as manifested by the loss of the granular layer
• Alternating collections of neutrophils are sandwiched between layers of parakeratotic stratum corneum, which is virtually pathognomonic for psoriasis
Histologic dermal findings include the following:
• Signs of inflammation can be observed throughout the dermis
• Marked hypervascularity and an increase in the size of the dermal papillae occur
• An activated CD3 + lymphocytic infiltrate is noted around blood vessels
• An aggregation of neutrophils in the dermis occurs that extends up into the epidermis
Management
Topical therapy
Topical agents used (often concurrently) to treat plaque psoriasis include the following:
• Corticosteroids
• Coal tar
• Anthralin
• Calcipotriene
• Tazarotene
Phototherapy
The 2 main forms of phototherapy are as follows:
• Ultraviolet B (UVB) irradiation - UVB therapy is usually combined with one or more topical treatments
• Psoralen plus ultraviolet A irradiation (PUVA) - This treatment uses the photosensitizing drug methoxsalen (8-methoxypsoralen) in combination with UVA irradiation to treat patients with more extensive disease