LGV is endemic in large parts of the tropics. Since 2003 anorectal LGV is also endemic among Men who have Sex with Men (MSM) throughout the industrialised world. Currently we see an increase in de incidence of LGV cases among MSM in Amsterdam. Occasional cases of heterosexual LGV are usually imported from endemic countries.

LGV is caused by Chlamydia trachomatis (Ct) biovar L. Compared to non-L biovar infections, LGV has a completely different clinical picture characterised by an invasive, lymph destructive and fibrosing inflammatory reaction. The majority of MSM with LGV are HIV co-infected (up to to 85%), and a considerable portion is hepatitis C co-infected.

LGV requires extensive treatment in contrast to non-L Ct infections, thus correct biovar identification is clinically relevant. Routinely LGV is excluded in Ct positive anal, ulcer, and bubo samples. Urethral LGV is not screened routinely. The vast majority of reported LGV cases comprise anorectal infections. Infections residing at other locations than the rectum could form an undiagnosed and undertreated reservoir contributing to ongoing LGV transmission. We recently found concurrent urethral LGV infections in 2.1% of MSM with anorectal LGV. Moreover, 6.8% of the partners of anorectal LGV cases had a urethral LGV infection. This shows that urethral LGV is common, probably key in transmission, and missed in current routine LGV screening algorithms.

In European MSM the majority of LGV infections is caused by biovar L2b (Amsterdam variant). Based on clonal relatedness of prevalent LGV strains, there is evidence that the LGV epidemic among MSM prevailed already in the United States in the 1980s and was introduced into Europe by the end of the last century via the highly internationalised network of sexual contacts among MSM. A new LGV variant was unveiled and designated L2c.