Psoriasis is an immune-mediated multifactorial hereditary skin disease. It can be induced by multiple factors for susceptible patients, such as trauma, infection and drug.

The disease takes on a genetic tendency, and environmental factors play a key role in inducing and worsening psoriasis. It is related to immune factors. For patients with psoriasis vulgaris, the lymphocyte and monocyte at skin lesion show apparent infiltration. Particularly, epidermal or dermal infiltration of T lymphocyte and dendritic cell is a main pathologic character of pathogenesis. Cytokines can stimulate cutin to form cell proliferation, and the latter releases vascular endothelial growth factor and angiogenesis to promote dermal angiogenesis, and accelerate and involve in the development of psoriasis.

Psoriasis is a systemic disease, and can be classified into vulgaris type, arfhropathica type, pustular type, and erythrodermic type according to clinical features. Over 99% psoriasis cases are vulgaris type, and most of other types are turned from vulgaris type.

(1) Topical medication therapy: glucocorticoid creams or ointments have remarkable curative effect, but attention should be paid to harmful reactions. Other drugs such as tretinoin also can be resorted to.
(2) Systemic drug therapy: tretinoins, immunosuppressant, etc.
(3) Biological agents (targeted immunomodulators): Biological agents are introduced for treatment of psoriatic arthritis and moderate to severe plaque psoriasis.
(4) Physical therapy: photochemotherapy.