Psoriasis, also known as clinical psoriasis, can be categorized into unusual, arthropathic, pustular, and erythrodermic types. Arm psoriasis begins with a long red papule or macular rash, but with different types, there is a certain variability in its initial symptoms. 1. Ordinary-type psoriasis: when it first grows, it mainly manifests as red papules or macules, and with the development of the disease, it can gradually expand into red patches with clear boundaries. 2. Arthropathic psoriasis: the lesions are similar to those of common psoriasis at the beginning, which are also red papules or macules, and can be accompanied by joint pain and swelling. 3. Pustular psoriasis: it can be divided into generalized type and limited type, in which generalized pustular psoriasis, mainly with acute onset, can appear on red papules or normal skin with pinpoint size, light yellowish shallow in the aseptic small pustules, densely distributed; 4. Erythrodermic psoriasis: mainly manifested as diffuse redness of the skin, infiltration and swelling and accompanied by a large number of furfuraceous scales. So once the skin on the arm appears above abnormal performance, pay attention to the hospital in time.