A. Early Stage
In acquired syphilis T.pallidum get into the skin through a micro-lesions or mucous membranes, usually through sex. The germs multiply, tissue reacts by forming infiltrates consisting of lymphocytes and plasma cells, particularly in the perivascular, small blood vessels proliferate, T.pallidum and surrounded by inflammatory cells. Treponema is located between the capillary endothelium and perivascular tissue around it. Loss of bleeding will cause erosion, on clinical examination appear as SI.