Malignant syphilis also called node-ulcerative syphilis or malignant lues, is an unusual but otherwise severe form of secundarism, that at present, is observed associated to pathologies such as diabetes, tuberculosis, malnutrition, alcoholism, drugaddiction, and to HIV positive patients. It is characterized by extended cutaneous polymorphous lesions that can be papules, plates, rounded tuberculous and ulceronecrotic lesions with a center covered by rupioid crusts surrounded by an eritematous overelevated border. They have small nodular involvement and serious general compromise that can expose the patient´s survival. A 43-years old female with mutilant ulceronecrotic lesions with rapid evolution and mucutaneous involvement, is presented. With clinical suspicion of secondary-tertiary syphilis, it was detected reactive serology to HIV infection. The recognition that a large proportion of patients with HIV infection also have syphilis has raised the watchword respect to the interaction between these two diseases.