Lymphogranuloma venereum is an infrequent sexually-transmitted disease caused by three distinct serovars of Chlamydia trachomatis (L1, L2 and L3) that primarily infect the lymphatic tissue. This infection can be transmitted through unprotected sexual contacts (either vaginal, oral or anal).
The most striking clinical manifestation of lymphogranuloma venereum among heterosexual individuals is tender unilateral inguinal and (sometimes) femoral lymphadenopathy. Proctocolitis, that mimics inflammatory bowel disease, is a common feature in homosexual populations, but also in women who have had rectal exposure. If not treated early, an invasive and systemic infection may ensue.
In the past, a plethora of synonyms have been used to describe this condition, such as climatic bubo, tropical bubo, poradenitis inguinalis, lymphopathia venereum, or Durand-Nicolas-Favre disease. Nevertheless, the designation lymphogranuloma venereum is a preferred term as it clearly differentiates this condition from another sexually-transmitted entity, granuloma inguinale.
The disease universally occurs in the tropical parts of Asia, Africa and South America, but since 2003 it has become endemic in Europe, North America and Oceania – most notably among men who have sex with men, and who exhibit high-risk sexual behavior. Lymphogranuloma venereum shows a peak incidence during the second and third decades of life.
Biology of the Causative Microorganism
Chlamydia trachomatis is the most common bacterial cause of sexually-transmitted diseases in both women and men. This is an obligate intracellular agent, which means that it requires a live cell to exhibit its pathogenicity (this characteristic makes it similar to viruses).
During its life cycle, Chlamydia trachomatis exhibits two different forms: the infectious form known as elementary body (EB), and non-infectious form known as the reticulate body. The size of its genome is 1042 kilobase pairs, which is about a quarter of Escherichia coli genome.
Furthermore, the organism is heat-labile and successfully inactivated within several minutes at 56 °C. On the other hand, infectivity can be maintained for several days at 4 °C. Chlamydia trachomatis is susceptible to ether, ethanol, as well as to low concentrations of formalin and phenol.
Based on the analysis of the chlamydial major outer membrane protein, this pathogen can be divided into 15 serovars: A-C (causing a serious eye infection known as trachoma), D–K (predominant in urogenital infections), and L1–L3 (responsible for lymphogranuloma venereum). Moreover, according to certain differences in amino acid components, the L2 serovar can be additionally separated into L2, L2’, L2a and L2b.
Pathophysiology of Lymphogranuloma Venereum
Lymphogranuloma venereum is principally a disease of the lymphatic tissue. As opposed to serovars A-K that are restricted to the mucosal tissue, aforementioned serovars L1-L3 induce a lymphoproliferative response after they enter the body via skin abrasions or skin breaks.
The affected regional lymph nodes become enlarged and undergo necrosis, which is followed by neutrophilic chemotaxis and abscess formation. These abscesses may coalesce and form multilocated abscesses, which then rupture and form fistulae and sinus tracts.
When the inflammatory process subsides with fibrosis, the obstruction of the subcutaneous and submucous lymphatic channels occurs, which results in lymphedema. If the regional blood supply is compromised, ischemic necrosis and superimposed skin ulceration may ensue.
The host immunity is known to inhibit chlamydial replication, but it often does not eliminate the microorganism, resulting in a latent state. This is the reason why it is of utmost importance to diagnose and treat this condition as soon as possible i.e., in order to avoid complications and potentially mutilating sequelae.
Reviewed by Afsaneh Khetrapal Bsc (Hons)