Dec. 8, 2013 at 2:49 PM ET

Jeff Swensen / for NBC News

The Mogul family at The Children's Institute in Pittsburgh, Pennsylvania where parents Stephen and Robyn have taken their daughter, Bari, 9 and Hayley, 15, to undergoing extensive therapy to help with their rare genetic disorders.

At 15, Hayley Mogul lacks the fine motor skills needed to write. Her sister Bari is 9 and still eating baby food.

There's no cure for their rare disorders, caused by unique genetic mutations. But for once, there's an advantage to having conditions so rare that drug companies cannot even think of looking for a cure. The sisters are taking part in a whole new kind of experiment in which scientists are literally turning back the clock on their cells.

Theyre using an experimental technique to transform the cells into embryonic form, and then growing these baby cells in lab dishes.

The goal is the get the cells to misfire in the lab in just the same way they are in Hayleys and Baris bodies. Its a new marriage of genetics and stem cell research, and represents one of the most promising applications of so-called pluripotent stem cells.

One day these two girls will probably change the face of medicine as we know it, said their father, Steven Mogul.

Steven and Robyn Mogul dont understand why both their daughters ended up with the rare mutations, which cause a range of neurological and metabolic problems.

We have been tested, said Mogul, a 45-year-old wealth manager living in Chicago. We dont have any mutations, and there are no developmental issues. We have no idea how it happened.

Link:
Stem cell science: Can two girls help change the face of medicine?