Synonyms Lymphogranuloma inguinale; lymphopathia venerea; poradenitis inguinalis; Durand-Nicolas-Favre disease; climatic Bubo; LGV " Cave: lymphogranuloma inguinale should not be confused with granuloma inguinale (donovanosis). Epidemiology Lymphogranuloma venereum (LGV) is endemic in Asia, Africa, South America, and the southeastern USA. In Europe, LGV infection is found almost exclusively in MSM, clinically presenting as proctocolitis, and is commonly associated with HIV. In a prevalence study, serovars L1-3 were found in 1.7% of HIV-positive MSM and 0.6% of HIV-negative or untested MSM. The vast majority of these men were asymptomatic (Lanjouw 2016; de Vries et al. 2015; Haar 2013). Etiopathogenesis The pathogen is Chlamydia trachomatis (serovars L1-L3, mostly 2b), a coccoid, obligate intracellular bacterium (chapter "▶ Gonorrhea and Urethritis"). Although the serovars A-K remain in the mucosa, the L-serovars are invasive organisms that spread in blood, cerebrospinal fluid and spleen already in the early phase of the disease. Chlamydia trachomatis attaches to the host cells through the main outer membrane protein, the heat shock protein 70, and heparin-like glycosaminoglycans. Clinical Features The clinical picture is divided into three stages. Stage I: Primary Lesion The incubation period is 2-6 weeks. First, an inflammatory papule of a few millimeters in size appears. This rapidly transforms into a vesicle, then into a papulopustule and finally ulcerates. The primary lesion is clinically unspecific and short-lived and therefore often unnoticed. The manifestations can be seen on the glans penis, in the coronary sulcus, in the prepuce or anterior urethral segment of men and in the vulva, in the vagina, or in the cervix of women. The primary lesion is painless and is therefore often not noticed. It heals spontaneously within 10-14 days. In the current LGV epidemic in Europe and North America among MSM, the rectum is the most common site of infection. In this context, the patients suffer from anorectal syndrome with severe pain, bleeding, abdominal pain, diarrhea, or constipation. The clinical picture is indistinguishable from that of a chronic inflammatory bowel disease, such as Crohn's disease or ulcerative colitis, and therefore often fails to be noticed. Asymptomatic courses, which are of epidemiological importance for the spread of the disease, have been proven. " If proctitis is present, LGV infection should always be excluded. Stage II: Buboes A bubo is an inflammatory lymph node that can develop in the context of an STI, but also in other infectious, autoinflammatory or tumorous diseases (Fig. 1). About 24 weeks after the onset of the primary lesion the