Psoriasis is a chronic, genetically influenced, remitting and relapsing scaly and inflammatory skin disorder that affects 1 to 3 percent of the world's population. The diagnosis is made on clinical grounds, although histologic examination of a skin-biopsy specimen may be helpful. Psoriasis is a disabling, though rarely life-threatening, disease with a social and economic impact that is underestimated by physicians and other health care providers. Recently, progress has been made in understanding the pathogenesis of psoriasis, and therapeutic advances are improving the care of even severely affected patients.

There are several types of psoriasis, including pustular, guttate, and arthritic variants. . . .