Ask the Doctors by Eve Glazier, M.D. and Elizabeth Ko, M.D

Rare STD Causes Inflammation of Urethra

Dear Doctor: My boyfriend and I were in London over the holidays, and we heard a lot about MG, a new sexually transmitted disease. Is it here in the United States too? Should I be worried?

Dear Reader: You're referring to Mycoplasma genitalium, also known as MG or Mgen. It's a bacterium that is transmitted through sexual contact, and as a result, can infect the reproductive tract. MG was first identified in the United Kingdom more than 30 years ago, so it's not really new. It was found in two men being treated for non-gonococcal urethritis, which is inflammation of the urethra, the tube that carries urine away from the bladder. "Non-gonococcal" means that the infection is not caused by the gonorrhea bacteria.

The Centers for Disease Control and Prevention only officially acknowledged the disease in 2015, so it's a fairly recent addition to the STD conversation. Although reliable statistics are not yet available, infection rates among women in the U.S. are estimated at about 1 percent. That's slightly higher than gonorrhea and lower than the rate of infection with chlamydia, which is 3 percent. However, when looking at high-risk populations, which constitutes young people who have multiple sexual partners and those who don't practice safe sex, some estimates of infection rates are as high as 20 percent.

Mycoplasma genitalium causes inflammation of the urethra in both men and women. Symptoms include an increased urge to urinate, as well as pain and burning, particularly during urination. Some cases are accompanied by an abnormal discharge. It's also possible for MG to produce no symptoms at all. A recent analysis of available data found that close to 60 percent of women who tested positive for MG had no symptoms. However, due to their reproductive anatomy, women face greater risks than men from infection. Among these is developing pelvic inflammatory disease, or PID, an infection of the female reproductive organs that can cause long-term health problems and can lead to infertility. The bacterium has also been linked to adverse birth outcomes, as well as to increased susceptibility to HIV infection.

Mycoplasma genitalium is challenging to diagnose. It lacks a cell wall, so it's not suitable for a gram stain, the most common technique for differentiating and identifying bacteria. It's so slow-growing that a culture takes six months to develop. Instead, nucleic acid amplification testing, or NAAT, which identifies the pathogen via its genetic material, is now being used. The test is typically done on urine in men and via cervical swabs in women. As with all bacterial infections, treatment is with antibiotics. And as with a growing number of bacterial pathogens, MG is developing antibiotic resistance.

As to whether people should be worried, if they have multiple partners and don't practice safe sex, the answer is yes. We're not referring only to MG infections when we say that. The number of new cases of sexually transmitted diseases, including chlamydia, gonorrhea and syphilis, reached an all-time high in 2017. That's part of a steep and sustained increase that has alarmed health care professionals. So, please, always practice safe sex. Anyone with any symptoms of a sexually transmitted disease should seek medical care immediately.

(Send your questions to, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)