Psoriasis a complex, chronic, multifactorial, inflammatory disease that involves hyperproliferation of the keratinocytes in the epidermis, with an increase in the epidermal cell turnover rate. Environmental, genetic, and immunologic factors appear to play a role. The disease most commonly manifests on the skin of the elbows, knees, scalp, lumbosacral areas, intergluteal clefts, and glans penis. Common types of psoriasis include the following:
Chronic stationary psoriasis (psoriasis vulgaris): Most common type of psoriasis; involves the scalp, extensor surfaces, genitals, umbilicus, and lumbosacral and retroauricular regions
Plaque psoriasis: Most commonly affects the extensor surfaces of the knees, elbows, scalp, and trunk.
Guttate psoriasis: Presents predominantly on the trunk; frequently appears suddenly, 2-3 weeks after an upper respiratory infection with group A beta-hemolytic streptococci
Inverse psoriasis: Occurs on the flexural surfaces, armpit, and groin; under the breast; and in the skin folds.
Pustular psoriasis: Presents on the palms and soles or diffusely over the body.
Erythrodermic psoriasis: Typically encompasses nearly the entire body surface area
Scalp psoriasis: Affects approximately 50% of patients.
Nail psoriasis: May be indistinguishable from, and more prone to developing, onychomycosis.
Psoriatic arthritis: Affects approximately 10-30% of those with skin symptoms; usually in the hands and feet and, occasionally, the large joints.
Oral psoriasis: May present as severe cheilosis, with extension onto the surrounding skin, crossing the vermillion border.
Eruptive psoriasis: Involves the upper trunk and upper extremities; most often seen in younger patients.
Management of psoriasis
 This may involve drugs, light therapy, stress reduction, climatotherapy, and various adjuncts such as sunshine, moisturizers, and salicylic acid.