1.Psoriasis vulgaris Clinical manifestations: the characteristics of the skin lesions are the main diagnostic basis of psoriasis vulgaris, manifested as red papules and plaques with extensive or restricted distribution, covered with silvery white scales; Auspitz’s sign can be positive. The course of the disease is chronic, and the lesions can subside after treatment, but they are prone to recurrence. Special types: acute punctate psoriasis: scaly papules 2-5 mm in diameter, often with sudden onset after acute infection; seborrheic psoriasis: moist, slightly greasy scaly red patches or plaques, often in typical areas of psoriasis or some flexural areas; reverse psoriasis: moist, slightly greasy scaly red patches or plaques in folds and some flexural areas; diaper psoriasis: psoriasis-like lesions in the infant diaper area. Histopathology: typical pathologic changes are informative in the diagnosis of common psoriasis. Pathological changes include: hyperkeratosis with hyperkeratosis, Munro microabscesses visible in the hyperkeratotic area, marked reduction or disappearance of the granular layer, thickening of the spinous layer, epidermal protrusions extending downward in the shape of pegs; pestle-shaped top of the dermal papillae, thinning of the spinous layer above them, dilated and congested capillaries, and infiltration of lymphocytes and neutrophils visible around them. Serological examination: In acute punctate psoriasis, serum anti-streptococcal hemolysin (anti-“O”) titers are often elevated. Diagnostic criteria: At present, the diagnosis of this disease is mainly based on clinical manifestations, and pathological changes can help to suggest the disease and differentiate it from other skin diseases. Diagnostic considerations: The disease is mainly diagnosed clinically and lacks specific examination methods. Diagnosis should be made in terms of lesion characteristics and disease course. A positive family history can help support the diagnosis of psoriasis, and pathological examination can help the differential diagnosis with other diseases. 2, pustular psoriasis Clinical manifestations: generalized pustular psoriasis: often acute onset, in common psoriasis lesions or normal skin without lesions quickly appear pinpoint to corn size, light yellow or yellow-white shallow in sterile small pustules, often densely distributed, can be fused to form lamellar pus lake. They are often accompanied by systemic symptoms such as chills and high fever, and may remit spontaneously, but may also recur in periodic episodes; limited pustular psoriasis: small pustules on the basis of symmetrically distributed erythematous plaques on the palms of the hands and plantars, occurring in batches, sometimes mild and sometimes severe, and persistent. Histopathology: The presence of spongy pustules in the upper epidermal spine layer (Kogoj micropustules) is of diagnostic importance for pustular psoriasis. The rest of the changes are the same as in common psoriasis. Serologic examination: Pan-onset pustular psoriasis may have increased peripheral blood leukocyte count and neutrophil ratio. Diagnostic criteria: At present, the diagnosis of the disease is mainly based on clinical manifestations, and pathological changes can help suggest the disease and differentiate it from other skin diseases. Diagnostic considerations: The disease is mainly diagnosed clinically and lacks specific examination methods. Diagnosis should be made in terms of lesion characteristics, disease course and patient’s systemic symptoms, and pathological examination helps to differential diagnosis with other diseases. 3, erythrodermic psoriasis Clinical manifestations: diffuse flushing and infiltration swelling of the whole body skin, between which there may be patches of normal skin (skin island), accompanied by large or fine bran-like flaking, palmoplantar may be glove or garter-like flaking, often accompanied by intense itching. It may be accompanied by systemic symptoms such as fever and superficial lymph node enlargement. The course of the disease is long and prone to recurrence. Histopathology: with pathological features of common psoriasis and chronic dermatitis. Serological examination: If there is fever and superficial lymph node enlargement, it may be accompanied by increased peripheral blood leukocyte count and neutrophil ratio. Diagnostic criteria: At present, the diagnosis of this disease is mainly based on clinical manifestations and previous history of common psoriasis. Diagnostic precautions: The disease is mainly diagnosed clinically and lacks specific examination methods. Diagnosis should be made from the characteristics of lesions, disease duration and past medical history. 4.Arthritic psoriasis Clinical manifestations: In addition to skin lesions, arthropathy can appear, and any joint can be involved, including the large joints of the elbows and knees, the small joints of the fingers and toes, the spine and the sacroiliac joints. It can be characterized by swollen and painful joints, limited movement, and in severe cases, joint deformities. Histopathology: The pathological manifestations of arthritic psoriasis lesions are the same as those of common psoriasis. Serological examination: If fever is present, it may be accompanied by an increased peripheral blood leukocyte count and neutrophil ratio. Rheumatoid factor is often negative. Diagnostic criteria: At present, the diagnosis of this disease is mainly based on clinical manifestations and the presence of psoriatic skin lesions. Diagnostic considerations: The disease is mainly diagnosed clinically. Negative rheumatoid factor helps to exclude rheumatoid arthritis. X-ray examination of the affected joints may be performed, showing loss of cartilage, osteoporosis, narrowing of the joint cavity with varying degrees of joint erosion and soft tissue swelling.