BOSTON (AP) – A rare sexually transmitted disease that can scar the genitals has been found in six patients in Massachusetts, health officials said.

Lymphogranuloma venereum, or LGV, is a form of chlamydia that can damage the bowels and scar the anus. The federal Centers for Disease Control and Prevention also have confirmed cases in San Francisco, Atlanta and New York.

So far, episodes in the United States appear to be limited to gay and bisexual men.

One patient told a doctor at the Fenway Community Health clinic in Boston that he probably caught the disease while visiting Brazil.

“This is probably a case of biological tourism,” said Dr. Daniel Cohen, a specialist in infectious diseases who has treated patients at the Fenway clinic.

Dr. Alfred DeMaria, the state’s director of communicable diseases control, said the disease’s reemergence may be a sign of unsafe sex.

“And that’s a concern in terms of other sexually transmitted diseases and HIV,” he said.

Unprotected anal intercourse is the key risk factor for the spread of LGV. Symptoms include painful rectal infections, but the first symptom may be a painless pimple or lesion on the genitals.

Dr. Hillard Weinstock, a medical epidemiologist at CDC, said the agency plans to work with state labs to set up testing for the disease.

If identified early, LGV can be treated with antibiotics. Untreated, it can cause permanent damage to the bowels and swelling and scarring of the genitals. Death is rare.

In the past two decades, LGV has primarily been found in the tropics. But in November, the Netherlands said 92 cases of LGV among gay and bisexual men had been reported there over the preceding year, compared to the usual two or three cases a year.