This type is the most common, and the damage can occur in all parts of the body, but the scalp, lumbosacral region, elbows and knees and extremities are the most common, often symmetrically distributed, and nails and mucous membranes can also be involved. The damage is a red papule of corn to green bean size, which gradually expands or fuses into a plaque with clear boundaries and obvious infiltration, with multiple layers of mica-like silvery-white scales on the surface, and lightly scraping the scales can reveal a layer of light red translucent film (film phenomenon), and then scraping the film, the dotted bleeding phenomenon (Ospitz’s sign) can be seen, which is the characteristic of this type. When the scalp is invaded, the thick scales make the hair into bundles, like a hairbrush, but do not cause hair loss, the scales cover the scalp, and the scabs are thickened like a helmet. About half of the patients have finger (toe) nail damage, which is characterized by thimble-like punctate depressions, longitudinal ridges, transverse grooves, clouding, hypertrophy, partial free end hypertrophy, hollow, or nail bed peeling, nail plate deformity or partial defects. Mucocutaneous psoriasis is less common and can occur on the head of the penis, as well as on the oral mucosa and conjunctiva. The course of the disease is chronic, and it mostly recurs or worsens in winter. It can be divided into progressive, quiescent and regressive phases. In the progressive phase, the skin sensitivity is high, and after trauma, needling or injection, psoriasis damage appears on the normal-looking skin there, which is called “isomorphic reaction”. After the lesions fade, hypopigmentation or hyperpigmentation may remain. According to the morphology of the lesions, they are classified into drippy psoriasis, coin-shaped psoriasis, map-shaped psoriasis, ring-shaped psoriasis and gyrus-shaped psoriasis, etc. There may be varying degrees of itchiness, and general health is not affected. After the acute drippy psoriasis subsides, some of them do not recur, while some lesions are confined to the scalp or elbows and knees, or some are stubborn and do not recede, and the lesions expand and fuse into coin-shaped, ring-shaped or map-shaped leathery and thick scaly plaques. Second, pustular psoriasis is rare, divided into two types of generalized and restricted: 1, generalized pustular psoriasis: more acute onset, soon generalized, accompanied by high fever, general malaise, increased white blood cells. The damage is the appearance of dense needle-sized to corn-sized shallow sterile pustules on the basis of erythematous plaques, with the flexural folds of the extremities being the most common, easily fused to form pus lakes, which can naturally resolve after 2 to 3 weeks, with the pustules drying, crusting and desquamating, but often with periodic recurrence. Some patients may have a furrowed tongue, and most patients also have pustules under the deck. Some people think that upper respiratory tract infection, topical drug stimulation or corticosteroid treatment can trigger this type of damage, and some scholars think that continuous limb dermatitis, herpes-like pustulosis and subangular pustular dermatosis, which occur in pregnant women, also belong to the category of pustular psoriasis. 2.Limited pustular psoriasis: mainly palmoplantar pustular psoriasis, also known as palmoplantar pustulosis and limited continuous acrodermatitis. Occurred in the palm, fish, metatarsal and heel lateral edge of the erythematous flaking area of the cluster, small deep in the sexual pustules, after absorption to leave brown spots. Arthritic psoriasis, also known as psoriatic arthritis: This type is uncommon, that is, psoriasis with joint symptoms similar to rheumatoid arthritis, mostly occurs after psoriasis, the two symptoms are often parallel, the end joints of the fingers and toes are common, red, swollen, painful, can also be deformed over time, ankylosis, serum rheumatoid factor is often negative, also commonly seen in pustular psoriasis. Fourth, erythrodermic psoriasis. Also known as psoriatic exfoliative dermatitis: Mostly caused by the external use of irritating drugs during the acute period, but also due to the long-term use of corticosteroids suddenly stopping the drug and lead to relapse, pan-pustular psoriasis repeated exfoliation can also present erythrodermic-like changes.