Rose Marie Bentley lived a relatively quiet life. She raised her family in the small town of Molalla, Oregon, where she taught Sunday school, sang in the church choir and earned a living selling farm and pet supplies.

But after Bentley died at the age of 99, a team of medical students studying her body in a lab learned that her life was a medical marvel.

Unbeknownst to Bentley, she was born with a rare condition called situs inversus with levocardia, which meant that several of her vital organs were positioned out of place. Her liver, stomach and other abdominal organs were transposed inside her body from right to left. However, her heart remained in its proper position to the left side of her chest.

The unusual condition affects about one in every 22,000 births and often leads to terminal cardiac problems. Doctors estimate that only one in 50 million people with the condition live to adulthood.

But Bentley beat the odds. Her family said she lived a long, healthy life and died without ever knowing she had the condition. The only ailment she suffered was arthritis.

“My mom would think this was so cool,” her daughter Louise Allee told the Oregon Health & Science University, which discovered the medical anomaly after Bentley’s body was donated for scientific research.

“She would probably get a big smile on her face, knowing that she was different, but made it through.”

A team of medical students made the unusual discovery last spring while examining Bentley’s body. Dr. Cam Walker, an assistant professor of anatomy, helped students overseeing the case.

After opening up Bentley’s body, the team realized that something was amiss.

“It took us a while to figure out how she was put together,” Walker said.

Upon further study, the team made the diagnosis. Bentley is believed to be the oldest person to live with the condition. Only two other patients with the condition are known to have lived into their senior years. Both died in their 70s.

Warren Nielsen, a medical student who worked on the case, described the finding as “amazing.”

“We were able to not only learn normal anatomy but also all the anatomic variation that can occur,” Nielsen said in a statement through the university. “I grew to appreciate how she was able to live as long as she did. It made me wonder who she was.”

None of Bentley’s children were born with transposed organs.

Bentley decided to donate her body to science before her death in 2017. The decision was inspired after she read the poem “To Remember Me – I Will Live Forever” by American poet Robert Noel Test. The poem describes the value of donating one’s body to “help others lead fuller lives.”

And that’s precisely what happened. Doctors say that the lessons they’ve learned from studying Bentley’s body will help in the treatment of future patients with the rare condition.