The Trebings are now speaking out about the emotional saga that prompted private doubts and public questions, coinciding with the release of a new book on the subject, "The Match."
"You want to make it go away," said mom Stacy Trebing. "You would do anything to cure her."
The Trebings learned, that even with treatment, DBF anemia often kills its victims by age 40. The only cure, doctors told them, was a bone marrow transplant from a genetically matched sibling.
So, decision one for the Trebings was: Would they try to give birth to a "savior" sibling for Katie?
The answer was a resounding yes.
"We had always wanted a third child," said Stacy Trebing. "So that was an easy decision."
What wasn't easy was the process to ensure that the new Trebing baby would be a genetic match for Katie.
It's called preimplantation genetic diagnosis and required that a number of Stacy's eggs be fertilized in a lab. A technician then removed a single cell from each embryo for genetic testing. The embryo that provided the exact match was then implanted in Stacy.
The result in May, 2005 was the Trebing's son, Christopher, a hearty kid the Trebings now call "Bubba."
Bubba's presence forced the Trebings to confront their second life and death decision: Whether to move forward with the bone marrow transplant for Katie.
"Doctors told us there was a ninety percent success rate," said Stacy Trebing. But the alternate outcome was chilling. If it failed, Katie Trebing could die.
"It was a rollercoaster," dad Steve Trebing said of the decision making process. "But in the end, we took the standpoint of, we're going to risk today for a better future."
"Some doctors told them not to do it. Some told them to do it. They had to make all these decisions themselves," said Beth Whitehouse, the Pulitzer prize winning journalist who authored "The Match."
The decision to move forward proved the right one. The bone marrow transplant cured Katie Trebing. But the Trebing's story has prompted questions about the future, ethical dangers of the technology they relied on to save Katie.
"Some of the possible uses of this technology seem disturbing, indeed awful to me," said Hofstra Law school medical ethics expert, Dr. Janet Dolgin.
Ethics experts like Dolgin fear future parents could use the genetic technology, not to cure disease but rather to create "super kids," with specific physical traits or even certain talents like athletic or musical prowess. Others raise questions about the disposal of fertilized embryos that don't fit a specific genetic need.
While this genetic process is regulated in Great Britain and Canada, there is no government regulation here. That's something Dolgin says needs to be considered.
The Trebings, however, have no regrets.
"Until you walk in someone else's shoes, it's so easy to cast judgment," said Steve Trebing.
Katie Trebing is now a rambunctious seven year old who loves soccer and cheerleading. The brother who saved her is about to turn five and is Katie's chess-playing partner.
"Life is so good," said Stacy Trebing. "Nothing can ruffle our feathers at this point."