[Infectious genital lesions].

External genital infections are multiple, possibly linked to viral, bacterial, mycosic, or parasitic infections. Viral and bacterial infections often integrate within the framework of Sexually Transmitted Diseases (STD/STI) and can be associated with a context of immunosuppression. Skin or mucosae damage is often isolated. Their diagnosis is often referred to clinically, and confirmed by local samples without the need for biopsy. Histological examination is indicated in unusual clinical cases or in cases of persistent lesions or atypical appearance or pseudotumoral, posing a challenge for clinical differential diagnosis. In these cases, the morphological analysis can be supplemented by special colorations, immunological techniques or even molecular analysis allowing in some cases the detection and identification of infectious agents. This chapter will integrate external genital infections of viral, bacterial and parasitic origin where histological analysis is the diagnostic element of orientation.