When an Oregon Health & Science University anatomy class opened 99-year-old Rose Marie Bentley’s chest cavity, something seemed amiss. It was only the beginning of what they would find.

Bentley’s heart was in the proper spot but all her other organs were transposed inside her body. Her spleen was on the right side instead of the left, her pancreas the opposite. And so on.

The students had just discovered a person so rare their teacher could find only two other people in medical literature who had made it to old age with the same condition -- situs inversus with levocardia.

One in every 22,000 people are born with the anomaly – and most tend to have heart defects that cause complications and illness.

The chance of making it to adulthood is one in 2.5 million. Living as long as Bentley did was a one in 50 million chance.

She was the oldest living person with situs inversus with levocardia. Perhaps most remarkable is that hardly anyone knew.

Bentley and her husband, who died 13 years ago, decided to donate their bodies to OHSU after they read a poem about how to remember loved ones.

After spending most of her adult life as a fixture in Molalla, where she sang in the local United Methodist choir, served as a Camp Fire leader, cultivated a large backyard garden and ran Bentley Feed Store with her husband, Bentley died Oct. 11, 2017, in Canby.

Louise Allbee, one of Bentley’s five children, said her mother would think this discovery was “so cool.”

“She would be tickled pink that she could teach something like this,” Allbee said. “She would probably get a big smile on her face knowing that she was different but made it through.”

Rose Marie Bentley of Molalla, who died at 99 years old, was the oldest living person with a super rare medical condition.

Bentley’s children didn’t know until OHSU reached out to learn more about her life and medical history.

Bentley once had her appendix taken out and the surgeon who performed the operation noted that it was found on the opposite side of where it was expected to be.

But that was the end of it.

“She likely did have an idea that was something was different in her anatomy,” said anatomy professor Cameron Walker. “I’m sure she didn’t have an idea of the full extent of her anatomic variation.”

Walker researched the condition and found two versions. In one, called situs inversus with dextrocardia, a person’s entire set of organs are a mirror image of most people’s, including the heart. There is a one in 10,000 chance of being born that way and most people with it live normal lifespans with few complications related to their strange anatomy.

But the chance of being born with transposed organs but a normal heart is even rarer – and more deadly. Just two other people with situs inversus with levocardia lived past middle-age, but they died in their 70s, Walker found.

He and his colleague Mark Hankin presented their findings on Bentley’s case to the 2019 American Association of Anatomists annual meeting this week. Walker said he hopes Bentley will have lessons for the medical community.

Among those, she can provide insights into what causes the condition. It’s unlikely that any of Bentley’s children have situs inversus from what Walker and OHSU doctors have taken away from conversations with them.

Walker thinks that situs inversus is likely a genetic condition, but how it passes on is still a mystery. He said it forms in the first two months of an embryo’s development, He hopes to learn more as he studies Bentley and other situs inversus cases.

He isn’t a medical doctor, but said that understanding differences in anatomy could have also led the surgeon who performed Bentley’s appendectomy to raise concerns that she might have other issues related to such an unusual condition.

But the experience for the students who were in Walker’s class might be the most important part of the stunning medical mystery.

They first found larger blood vessels were returning to the heart in a way that isn’t normally true for most people. By the end of class, they were part of a major medical landmark.

The journey of detection and diagnosis -- even in more mundane cases -- can teach students to be smarter and more compassionate health care providers, Walker said.

Bentley had seen all 50 states and left the family Molalla feed store to her grandchildren. She lived a long, happy life, according to her children.

But Walker said she still has a lot to contribute to the world, including why she was so unique.

“That will be part of the puzzle,” Walker said.