Pityriasis rubra pilaris (Pityriasis rubra pilaris), also known as Pityriasis pilaris (Pityriasis pilaris) damage is characterized by scaly erythema of the skin, and later the appearance of clusters of follicular papules, and papules are fused with each other like psoriasis-like plaques, often accompanied by palmoplantar keratosis. In Chinese medicine, it is equivalent to fox urine prick. (I) Pathogenesis The etiology of the disease is still unclear, the disease can be divided into family type and acquired type two, the former is often onset in childhood, the latter can occur at any age, men and women can be ill. Family type is autosomal dominant. According to Leitner’s statistics, 64 (51%) of the 125 cases of this disease have a positive family history. In addition, it has been found that there is a special acidic keratin (K17) in damaged skin, which is not found in normal skin. (ii) Pathogenesis The pathogenesis is still unclear. scholars such as Porter found that the epidermis in this disease is hyperproliferative, and the conversion time of 1AC-labeled methionine and glycine through the epidermis is shortened. Epidermal hyperactivity, labeling index increased, for the average normal value of 3% to 27.3% ± 8.6%, hairy erythema epidermis generation rate is significantly faster than normal skin, but generally slower than psoriasis or similar to it. And the growth rate of nails is lower than psoriasis, but faster than normal. Some scholars have proposed that this disease is related to the patient’s hypothyroidism or adrenal pituitary system dysfunction affecting the metabolism of vitamin A in the blood, or with the patient’s serum vitamin A acid binding protein synthesis defects. In addition, liver and kidney dysfunction, tuberculosis, tonsillitis, cold and flu can also induce this disease, but have not been confirmed.