LGV and ordinary chlamydia are caused by the same bacterium — Chlamydia trachomatis — but different strains. LGV comes from the more aggressive L1–L3 serovars and causes severe, invasive disease like rectal inflammation or swollen groin glands; regular chlamydia (serovars D–K) is usually mild or silent. The big practical difference: LGV needs a much longer antibiotic course.
aggressive chlamydia; 21-day doxycycline
~1.65M US cases/yr; cured with doxycycline
| Item | Value |
|---|---|
| Lymphogranuloma venereum (LGV) | curable — aggressive chlamydia; 21-day doxycycline |
| Chlamydia | curable — ~1.65M US cases/yr; cured with doxycycline |
What each one is
Lymphogranuloma venereum (LGV)
LGV is an aggressive form of chlamydia caused by Chlamydia trachomatis serovars L1, L2, or L3 CDC LGV. These strains behave differently from the ones behind everyday genital chlamydia — instead of staying on the surface of the genital or rectal lining, they invade the lymphatic tissue and trigger deep, destructive inflammation. That's why LGV produces swollen lymph nodes and ulcerating disease rather than the mild irritation most people associate with chlamydia. Recent outbreaks have clustered among men who have sex with men, often among people also living with HIV.
Chlamydia
Chlamydia is caused by the same bacterium, but the strains responsible for most US genital infections are serovars D–K CDC. It's the most-reported STI in the country — roughly 1.65 million cases in 2023, or 492 per 100,000 people, a number that's stayed fairly flat from 2020 through 2023 CDC AtlasPlus, 2023. These strains stay near the surface and cause far less tissue damage, which is part of why so many infections go unnoticed.
Symptoms compared
Ordinary chlamydia is famously quiet. About three quarters of infected women and half of infected men have no symptoms at all. When symptoms do show up in women, they include abnormal vaginal discharge and burning on urination; if the infection climbs higher, it can cause lower abdominal or low-back pain, fever, pain during intercourse, and bleeding between periods.
LGV tends to make itself known, and it does so in one of two patterns. The most common today is proctocolitis — inflammation of the rectum and lower colon — with mucoid or bloody rectal discharge, anal pain, constipation, fever, and tenesmus (a constant, frustrating urge to pass stool even when the rectum is empty). The second pattern, more typical in heterosexual patients, is tender, usually one-sided swelling of the lymph nodes in the groin (the inguinal or femoral nodes). That swelling can progress to buboes — fluctuant, pus-filled lumps that can rupture if untreated. You can read more on the full range of presentations under lgv symptoms.
How to tell them apart
Here's the honest answer: you usually can't tell them apart by feel. Rectal chlamydia and rectal LGV can both cause discomfort and discharge; the overlap is real, and a worried person guessing from symptoms alone will often be wrong. A test is what settles it.
That said, certain features push a clinician toward LGV rather than ordinary chlamydia. Severe proctocolitis with bloody discharge and tenesmus is a red flag. So is a tender, one-sided groin swelling — that's almost never plain genital chlamydia. Risk context matters too: a person with receptive anal exposure, an outbreak setting, or HIV coinfection raises the index of suspicion. Standard chlamydia, by contrast, is more likely to be silent or to cause only mild discharge and burning.
LGV vs regular chlamydia at a glance
| Regular chlamydia | LGV | |
|---|---|---|
| Bacterium | C. trachomatis serovars D–K | C. trachomatis serovars L1–L3 |
| Severity | Mild, often silent | Aggressive, invasive inflammation |
| Typical symptoms | Discharge, burning on urination, often none | Proctocolitis (bloody/mucoid discharge, tenesmus) or one-sided groin swelling/buboes |
| Most-affected groups | Anyone sexually active | Men who have sex with men, often with HIV; groin form more common in heterosexual patients |
| Testing | NAAT at the relevant site | NAAT at the symptomatic site plus clinical suspicion |
| Treatment | Doxycycline 100 mg twice daily for 7 days | Doxycycline 100 mg twice daily for 21 days |
Testing
For both, the recommended method is a nucleic acid amplification test (NAAT), which detects the bacterium's genetic material and is the optimal test for genital and extragenital infection CDC. In practice that means a urine sample, a self-collected swab, or a quick clinical exam, depending on the site being checked. Many people get this free or low-cost at health departments, Planned Parenthood, and Title X clinics.
LGV adds a wrinkle. Routine NAATs confirm C. trachomatis but don't always distinguish the L serovars from the ordinary ones, so the diagnosis rests on clinical suspicion plus a NAAT taken at the symptomatic site — for example, the rectum — with other causes ruled out. If you have rectal or groin symptoms, tell the clinician exactly what and where, so they swab the right place. You can get tested at a clinic or order a test, and if you're timing things around a recent encounter, see when to test after exposure.
Treatment compared
Both are treated with doxycycline, but the duration is the headline difference. Ordinary chlamydia is treated with doxycycline 100 mg orally twice daily for 7 days CDC 2021. The 2021 guidelines made doxycycline first-line over the old single-dose azithromycin after a randomized trial found doxycycline cleared rectal chlamydia far better — 100% cure versus 74% with azithromycin RCT.
LGV needs a substantially longer course: doxycycline 100 mg orally twice a day for 21 days. The extended duration is deliberate — the L serovars invade deeper tissue and lymph nodes, so a short course doesn't fully clear them. Stopping early, or treating LGV as if it were routine chlamydia, risks leaving infection behind and allowing complications. Finishing the full 21 days matters.
Partner treatment matters for both. In a landmark trial, giving patients medication to deliver to their partners — expedited partner therapy — measurably cut persistent or repeat infection, with the largest benefit for gonorrhea (3% vs 11%) NEJM EPT trial. Making sure partners are treated is also how you avoid chlamydia reinfection after you've finished your own course.
Can you have more than one at once?
Yes. Because LGV and ordinary chlamydia are the same species, a single NAAT will flag chlamydia in either case, and a person can carry strains at more than one site — say, genital and rectal — at the same time. Coinfection with other STIs is also common, particularly HIV in the populations where LGV outbreaks have occurred. That's why a clinician seeing LGV-type symptoms will typically test broadly rather than assume a single diagnosis.
When to see a clinician
See a clinician promptly if you have bloody or mucoid rectal discharge, significant anal pain, a constant urge to pass stool, or a tender lump in the groin — these point toward LGV and need the longer treatment course. Don't wait it out. For milder symptoms, or no symptoms after a possible exposure, routine testing is still the move. Untreated chlamydia can spread and cause pelvic inflammatory disease and fertility problems, and untreated LGV can scar lymphatic tissue, so neither is worth ignoring.