Mucocutaneous rashes are most often seen in syphilis and occur on the chest, abdomen, flanks and back of the trunk, but rarely on the face. Syphilitic pustules can occur in weak and malnourished patients, often with high fever and systemic symptoms. The causes of mucocutaneous rash, which is also the cause of syphilis, are: Etiology: The causes of syphilis include congenital syphilis and acquired syphilis. The main direct transmission through sexual intercourse, partly indirect contact transmission, that is, the sharing of clothes, towels, toothbrushes, razors, utensils, etc. transmission. Blood transfusion and breastfeeding can also be transmitted. In pregnant women with syphilis, the syphilis spirochete can enter the fetus through the placenta and infect the fetus. The onset of syphilis is closely related to the proliferation of syphilis spirochetes in the body and the immune response they cause in the host, which can be latent in the body after infection and develop when the immune system decreases. Syphilis is a chronic disease. Despite the presence of a large number of syphilis spirochetes in the initial damage. However, syphilis is not a simple inflammatory response due to the release of toxic or inflammatory substances or the direct presence of syphilis spirochetes in the tissues. Within the cellular infiltrate of the primary injury, monocytes predominate in the acute inflammatory response, with polymorphonuclear leukocytes taking precedence. In the early stages of syphilis infection a large number of syphilis spirochetes are present outside the cells in close proximity to the blood vessels.