The Food and Drug Administration (FDA) is warning diabetes patients that some drugs may cause a flesh-eating bacterial infection of the genitals.

The FDA issued the warning on Wednesday. Cases of Fournier’s gangrene have been reported in connection with sodium-glucose cotransporter-2 (SGLT2) inhibitors.

The drugs help the body lower blood-sugar levels via the kidneys, and excess sugar is excreted in a patient’s urine. Urinary tract infections are a known side effect.

The SGLT2 inhibitors approved by the FDA include Johnson & Johnson’s Invokana, Eli Lilly & Co’s Jardiance, as well those from Bristol-Myers Squibb, AstraZeneca Plc, Merck & Co and Pfizer Inc.

Patients are at risk for an infection known as Fournier’s gangrene, an extremely rare but life-threatening bacterial infection of the tissue under the skin that surrounds muscles, nerves, fat, and blood vessels of the perineum. The FDA said the bacteria usually gets into the body through a cut or break in the skin. 

While having diabetes is a risk factor for the infection, it is still rare. Publications report Fournier’s gangrene occurs in 1.6 out of 100,000 males annually in the U.S., and most frequently occurs in males 50-79 years.

The FDA said in the five years from March 2013-May 2018, they identified 12 cases of Fournier’s gangrene in patients taking one of the inhibitors. This is compared to only six cases identified in a review of other antidiabetic drug cases over a period of more than 30 years.

The cases included 7 men and 5 women. All of the patients were hospitalized and required surgery.

The FDA said some patients required multiple disfiguring surgeries, some developed complications, and one patient died.

The FDA is concerned there may be additional cases that they are not aware of. Patients should seek medical help immediately if they experience any symptoms of tenderness, redness, or swelling of the genitals or the area from the genitals back to the rectum, and have a fever above 100.4 F or a general feeling of being unwell.