Lymphogranuloma venereum (LGV)

Chlamydia trachomatis has many strains. Most cause surface infection of the genital tract, rectum, throat or eye. LGV strains, designated L1, L2 and L3, behave differently: they travel into lymph nodes and deeper tissue, which is why they can cause painful swollen glands and, if left untreated, lasting damage to the rectum or genitals.

NHS Inform describes LGV as rare in Scotland and found mainly in men who have sex with men. Because the infection often produces no symptoms, it can be passed on without either partner realising.

DermNet describes three stages in classical LGV. In the first, a small and usually painless papule or ulcer appears three to six weeks after infection and is easily missed. In the second, two to six weeks later, painful swollen lymph glands develop in the groin and may form buboes that rupture and drain. In the late stage, untreated infection can cause fistulas, rectal strictures, infertility and genital deformity.

When the rectum is infected, as is common in current outbreaks, people may notice bloody or pus-like anal discharge, pain on opening the bowels or during receptive anal sex, constipation, or a feeling of incomplete emptying.

• Swollen lymph glands in the groin.

• Ulcers or sores on the genitals or around the anus.

• Blood or pus from the back passage and rectal pain.

• No symptoms at all in a substantial number of people.

Testing starts with a nucleic acid amplification test for chlamydia on a swab from the affected site or on urine. If chlamydia is detected, the laboratory carries out further DNA testing to see whether it is an LGV strain. NHS Inform advises that the final result can take up to three weeks, and that doctors may therefore begin antibiotics before it is known.

The NHS explains that STI tests may not turn positive until up to seven weeks after sex, and that sexual health clinics offer testing without a GP referral, with confidential records that are not shared with a GP unless you ask.

LGV is treated with antibiotics. DermNet reports that doxycycline or erythromycin for at least three weeks is needed, with alternatives such as moxifloxacin where resistance occurs and azithromycin sometimes used where adherence to a longer course is a concern. A standard chlamydia regimen, which the NHS describes as a single dose or tablets for seven to fourteen days, is shorter than LGV treatment.

Treatment is led by sexual health clinics. Abstaining from sex until treatment is completed and until partners have been treated reduces the chance of reinfection and onward spread.

Partners from the preceding three months should be tested, and clinics can help to inform partners anonymously if you prefer. NHS Inform recommends that people diagnosed with LGV are also tested for gonorrhoea, syphilis and HIV, since infections often occur together.

Follow-up tests are arranged to confirm that the infection has cleared, particularly because rectal symptoms may take time to settle.

Long-standing infection can lead to scarring, genital swelling, rectal damage with bowel problems and, rarely, spread through the bloodstream causing inflammation of joints or liver. Prompt diagnosis and the complete antibiotic course make these outcomes uncommon.

Condoms for vaginal, anal and oral sex reduce the risk, as does regular STI screening if you have new or multiple partners. Anyone with rectal symptoms after sex should be tested rather than waiting for them to settle. Advice and testing are available through NHS sexual health services.