Mycoplasma genitalium (Mgen) shows up differently by sex. In men it usually causes urethritis, with discharge and burning during urination that tends to linger or come back. In women it more often causes cervicitis that can climb into the pelvis. In both the infection is frequently silent, and women are especially likely to carry it with no symptoms at all.
rising — guides therapy
doxy → moxifloxacin
| Item | Value |
|---|---|
| US adults infected | ~1–2% |
| Azithromycin resistance | ~50% — rising — guides therapy |
| Often | no symptoms |
| Treatment | resistance-guided — doxy → moxifloxacin |
What is Mgen, and why does it behave differently in men and women?
Mgen is a tiny, slow-growing bacterium that lacks a cell wall, so penicillins and cephalosporins, the antibiotics that attack cell walls, do nothing against it CDC, 2021. It's an emerging cause of urethritis in men and cervicitis in women, and it infects the lining of the genital tract. Because the male urethra is a narrow tube that funnels every irritation into a noticeable symptom, men are more likely to feel something. The cervix can be inflamed without producing any sensation, so women often have no clue they're infected. For the bigger picture, see our overview of mycoplasma genitalium.
The common symptoms (and what each one feels like)
When Mgen does cause symptoms, they overlap heavily with chlamydia and gonorrhea, so it gets missed. The core complaints are:
- Dysuria — a burning or stinging sensation during urination, caused by inflammation of the urethral or cervical lining.
- Abnormal discharge — thin, sometimes cloudy fluid from the penis or an unusual change in vaginal discharge as the cervix becomes inflamed.
- Pelvic or lower-abdominal discomfort, more typical in women as inflammation moves beyond the cervix.
- Bleeding between periods or after sex in women, a classic sign that the cervix is irritated and friable.
- Persistence is the tell. Mgen urethritis or cervicitis that doesn't clear with standard treatment, or that keeps returning, points to this organism.
Symptoms specific to men vs women
Symptoms in men
In men, Mgen is a leading cause of non-gonococcal urethritis, meaning inflammation of the urethra not caused by gonorrhea. That means urethral discharge and burning with urination, often a mild but nagging irritation rather than the dramatic flood seen with gonorrhea. It's frequently persistent or recurrent: a man may get treated for "urethritis," feel better briefly, then have symptoms creep back because the bacterium was never the chlamydia or gonorrhea he was treated for.
Symptoms in women
In women, Mgen targets the cervix, causing cervicitis. That inflammation can produce abnormal discharge, bleeding between periods or after sex, and sometimes discomfort. Left unchecked, it can ascend into pelvic inflammatory disease (PID), an infection of the uterus, fallopian tubes, and surrounding pelvic organs. Women are far more likely than men to carry Mgen with no symptoms whatsoever, which lets the infection persist silently and raises the stakes for downstream harm.
What about throat and rectal symptoms?
Mgen's best-established disease is genital, in the urethra and cervix. Throat and rectal carriage are less well characterized than for gonorrhea or chlamydia, and there's no standard symptom picture or routine testing protocol for those sites. If you have rectal symptoms after receptive anal sex, raise it with your clinician directly so the right swab can be chosen, rather than assuming a urine test covers it.
How soon do Mgen symptoms appear?
There's no single tidy incubation number to quote. The timing varies, and because so many infections are silent, the onset you notice may be far removed from when you were exposed. If you've had a recent exposure and want to time things sensibly, read our guide on when to test after exposure so you don't test too early and get false reassurance.
What Mgen gets mistaken for
Because the symptoms are nonspecific, Mgen routinely masquerades as other conditions and gets treated as them:
- Chlamydia or gonorrhea — same burning, same discharge, but a standard STI panel doesn't include Mgen, so it's missed.
- A urinary tract infection — the burning with urination overlaps, leading to antibiotics that don't touch the real organism.
- In women, the bleeding and discharge of cervicitis can be chalked up to a yeast infection, bacterial vaginosis, or hormonal spotting.
- "Treatment-resistant" urethritis — when symptoms persist after standard therapy, Mgen is one of the prime suspects.
Complications and when symptoms become urgent
Untreated Mgen carries real consequences, especially in women. The main complications are:
- Pelvic inflammatory disease (PID) — infection spreading to the uterus and fallopian tubes, which can cause scarring and chronic pelvic pain.
- Infertility — Mgen is associated with about a twofold increased risk in women, largely through that tubal damage.
- Preterm delivery — an increased risk in pregnancy.
- In men, persistent or recurrent urethritis that refuses to resolve.
Seek prompt care for fever, severe or worsening lower-abdominal or pelvic pain, pain during sex, or any pregnancy with these symptoms. Those can signal PID, which needs urgent treatment to protect fertility. The full rundown lives in our piece on mgen complications.
Who should get screened?
There's no recommendation to screen asymptomatic people for Mgen, and routine, population-wide testing isn't advised. Testing is reserved for people who have a reason: persistent or recurrent urethritis in men, cervicitis or signs of PID in women, and partners of someone diagnosed. Throwing a Mgen test at everyone would surface harmless carriage and drive needless antibiotic use, the opposite of what we want with a resistant organism.
Why resistance makes the right test matter
Mgen has quietly become a resistance problem. Macrolide-resistance mutations now exceed half of isolates in many areas — over 62% in one US STI clinic — so the old single dose of azithromycin frequently fails NYSDOH/Hopkins. Current practice is resistance-guided: doxycycline first to lower the bacterial load, then azithromycin if the strain is macrolide-susceptible or moxifloxacin if it's resistant. That's only possible with a specific M. genitalium test, and a standard STI panel won't find it. awareness is key in mg diagnosis and treatment.
How is Mgen confirmed?
Diagnosis is made from a simple sample — a urine cup, a self-collected swab, or a quick exam — using a specific molecular (NAAT) test for Mgen, with results usually back in a few days and often free or low-cost at health departments, Planned Parenthood, and Title X clinics. You have to ask for the Mgen-specific test by name. Start with our practical guide to get tested.
When to see a clinician
Make an appointment if you have burning with urination, abnormal discharge, bleeding between periods or after sex, pelvic pain, or urethritis that came back after treatment, or if a partner was diagnosed. This diagnosis is common and treatable, and clinics handle it daily. The goal is to match the right antibiotic to the right strain, so pushing for the specific test pays off.