LGV is chlamydia's nastier cousin — primarily in MSM. It needs 21 days of doxycycline (not the standard 7). Misdiagnosis as IBD is common. Here's the practical guide.

LGV (Lymphogranuloma Venereum) — The Rising MSM STI

LGV (lymphogranuloma venereum) is caused by specific serovars of Chlamydia trachomatis (L1, L2, L3) — distinct from the strains causing typical chlamydia. It causes severe rectal disease, especially in MSM (men who have sex with men), and has been rising in US/European outbreaks since the 2000s.

LGV requires longer treatment than standard chlamydia. Misdiagnosis as inflammatory bowel disease (IBD) is common. Here's the practical picture.

The short answer

What it is: Chlamydia trachomatis L-serotype infection
Main population affected: MSM, particularly HIV+ MSM with high partner counts
Main presentation: Severe rectal inflammation (proctocolitis) with rectal pain, discharge, bleeding, fever
Diagnosis: Rectal swab → chlamydia NAAT → genotype testing for L-serovar (when LGV suspected)
Treatment: Doxycycline 100 mg twice daily for 21 days (NOT the 7 days for standard chlamydia)
Misdiagnosis: Often confused with IBD or cancer; can lead to unnecessary procedures

What LGV looks like

Stage 1: Primary lesion (often missed)

Small painless ulcer or papule at site of infection
Typically at rectum, genitals, or oral mucosa
Resolves on its own in days to weeks
Often not recognized as STI

Stage 2: Lymph node involvement

"Buboes" — swollen, sometimes tender lymph nodes
Inguinal (groin) area most common for genital LGV
Less common in rectal LGV

Stage 3: Rectal LGV (most common presentation in MSM)

Proctocolitis: rectum and colon inflammation
Severe rectal pain
Bloody or mucous rectal discharge
Sensation of needing to defecate (tenesmus)
Constipation alternating with diarrhea
Sometimes fever
Sometimes anal/perianal ulcers
Lymph node swelling around rectum (palpable on exam)

Late complications (untreated)

Rectal strictures
Fistulas
Permanent lymph node damage
Chronic pain

Who's at risk

High-risk groups

MSM with multiple recent partners — primary risk
HIV+ MSM — significantly elevated risk
Those engaging in receptive anal sex with multiple partners
Travelers to areas with LGV outbreaks (Europe, US major cities)

Lower risk

Women — less commonly affected
Heterosexual men — rare

Why it's often misdiagnosed

LGV proctocolitis can look exactly like:

Inflammatory bowel disease (IBD) — Crohn's or ulcerative colitis
Rectal cancer
Other infectious proctocolitis (gonorrhea, herpes, syphilis)

Patients sometimes go through:

Colonoscopy with biopsy
IBD diagnosis and treatment
Months of immunosuppression
Worsening symptoms
Finally getting LGV diagnosis

This is why testing for LGV in MSM with rectal symptoms is so important.

How LGV is tested

Step 1: Standard chlamydia NAAT

Rectal swab → tests for chlamydia
Positive for chlamydia → could be standard strain or LGV

Step 2: LGV genotyping

Sample sent to specialty lab
Determines if L-serovar is present
Not always done routinely — must be specifically requested

When to specifically request LGV testing

Severe rectal symptoms (proctocolitis)
Rectal chlamydia positive in MSM with symptoms
Inguinal lymphadenopathy in genital infection
Symptoms not responding to standard chlamydia treatment
High clinical suspicion in high-risk population

Treatment

Standard regimen

Doxycycline 100 mg twice daily for 21 days
21 days — significantly longer than standard chlamydia (7 days)
Treatment must complete the full course

Alternative regimens

Azithromycin 1 g weekly for 3 weeks — if doxycycline can't be used
Erythromycin 500 mg four times daily for 21 days

In pregnancy

Erythromycin 500 mg four times daily for 21 days (doxycycline is contraindicated)
Azithromycin 1 g weekly for 3 weeks may be alternative

Failure rates

~5-10% of cases don't respond to first-line treatment
Re-evaluation, longer course, or alternative antibiotics for persistence
Specialty consultation if standard treatment fails

After treatment

Test of cure NOT routinely needed unless symptoms persist
Partners need treatment — all sexual contacts from past 60 days
Avoid sex for 7 days after starting treatment
Re-test at 3 months for reinfection
HIV testing strongly recommended at diagnosis if not recent

Partner notification

All sexual partners from past 60 days should be tested AND treated
"Expedited partner therapy" sometimes appropriate but often complex for LGV (longer regimen)
HIV status of partner(s) also relevant

LGV in 2026 — the epidemiology

Outbreaks in major US cities continued through 2010s and 2020s
Predominantly in MSM
Often co-infection with HIV (50-80% in some cohorts)
DoxyPEP (used for general bacterial STI prevention) may reduce LGV incidence — see doxyPEP
Public health surveillance continues; LGV reportable in many jurisdictions

Prevention

Same as for general STIs

Condom use during anal sex
Partner discussions and disclosure
Routine STI screening
HIV PrEP (for HIV-negative MSM)
DoxyPEP for eligible MSM

Specific to LGV

Awareness in high-risk populations
Prompt evaluation of rectal symptoms
Avoid sharing sex toys without cleaning
Avoid fisting / extensive rectal contact during peak outbreak periods

Differential diagnosis

If you have rectal symptoms, the differential includes:

LGV proctocolitis
Standard chlamydia proctitis
Gonorrhea proctitis
Herpes proctitis
Syphilis (anorectal chancre)
Inflammatory bowel disease (Crohn's, ulcerative colitis)
Rectal cancer
Anal fissure
Hemorrhoids with infection
Trauma (e.g., from anal sex)

Proper evaluation includes:

Rectal swab for chlamydia/gonorrhea NAAT
HSV and syphilis testing if ulcers
Visual examination
Sometimes flexible sigmoidoscopy for severe symptoms

What to ask your provider

"Can you specifically test for LGV? I have rectal symptoms and I'm in a higher-risk group."

"If positive, will I get the 21-day course?"

"What's the protocol for partner notification?"

"Am I a candidate for doxyPEP or PrEP going forward?"

Common misconceptions

"LGV is rare and exotic — I don't need to worry." Outbreaks have been ongoing in major US/European cities for 20 years. If you're MSM with rectal symptoms, ask.

"Chlamydia treatment will cover it." Standard 7-day treatment is insufficient for LGV. 21 days is needed.

"I don't have symptoms — I'm fine." Asymptomatic LGV is possible, especially in early stages. Routine extragenital STI screening matters.

"LGV is just severe chlamydia." It's a distinct entity with longer treatment, different complications, and different epidemiology.

Bottom line

LGV is:

A serious form of chlamydia affecting mostly MSM
Causes severe rectal inflammation that can mimic IBD or cancer
Diagnosed with rectal NAAT + LGV genotyping (must be specifically requested)
Treated with 21 days of doxycycline (NOT 7)
Reportable in many jurisdictions
Worth specifically requesting testing for if you're MSM with rectal symptoms

If you're MSM and have severe rectal symptoms — discharge, bleeding, pain, fever — make sure LGV is on your provider's radar. The earlier it's identified, the easier it is to treat. Untreated, it can cause permanent complications.