For most people, a uniboob is a sports bra problem. Swap the bra, problem solved. But for some, it’s a permanent fixture—a medical condition called symmastia, where the breasts fuse at the center of the chest and create a single, continuous mound.

Yes, it has a nickname. Doctors call it “bread-loafing.” Make of that what you will.

Symmastia comes in two forms. The first is congenital, meaning you’re born with it. In these cases, a web of skin, fat, and tissue extends naturally over the sternum, erasing the boundary between the breasts. Genetics is thought to play a role, though doctors don’t fully understand why it happens. English TV personality Charlotte Crosby, known from MTV’s Geordie Shore and Celebrity Big Brother, has spoken openly about her congenital symmastia—a condition her mother also has. “If a picture of me is online, people say things like ‘What is wrong with her boobs? They’re deformed! They’re stuck together,” she told Heat magazine.

Acquired symmastia is almost exclusively a surgical complication. When implants are too big for someone’s frame, sit too close to the center, or land in a poorly constructed pocket, they can slowly work their way inward until they meet. A narrow breastbone raises the odds, and so does pectus excavatum, where the sternum caves in instead of sitting flat. Swelling after surgery confuses things—some patients are weeks into recovery before anything looks obviously wrong.

Uniboob Isn’t Dangerous. It Does Suck Though.

Symmastia generally isn’t dangerous. It doesn’t affect the heart or lungs, and it’s not life-threatening. But it can cause skin irritation from friction at the chest’s center, and for many patients, the emotional weight is significant. Crosby has said the condition makes her feel “under-confident” and limits her wardrobe options.

A compression bra can occasionally correct the issue if it’s caught right after surgery. Most cases, though, need more. Surgery, sometimes multiple rounds, is usually required, with options ranging from liposuction and tissue excision to internal sutures or revision surgery to reposition or replace implants.

The Real World alum Flora Alekseyeun, who developed symmastia after three procedures and sought corrective surgery on Botched, explained: “Before my surgery, I had a uniboob situation that was not sexy at all. Now, thanks to Dr. Dubrow, I have two separate breasts.”

The best prevention for surgical cases: an experienced, board-certified plastic surgeon and implants matched to your actual anatomy. The uniboob isn’t a look anyone is going for on purpose.