Two-year-old Aubree Dunn of Iowa City can rattle off the alphabet and has no problem counting to 20. If you ask, she'll even sing the Barney song or "Twinkle, Twinkle, Little Star." But what is most remarkable about the toddler is that she is alive to do all these things.

If it had not been for a perfect stranger, Tom Sandersfeld of Marengo, Iowa, Aubree likely would not be here today. Sandersfeld donated the bone marrow that saved Aubree's life.

"He's a miracle to us, an angel sent from heaven," said Aubree's mom, Bev Dunn, just before meeting Sandersfeld for the first time.

The Dunn/Sandersfeld meeting took place Friday, Nov. 12 at the second annual reunion for bone marrow donors and recipients at the University of Iowa. The Dunn and Sanderfeld families were among the 400 people expected at the event.

Although the reunion was a time when donors and recipients could come together to celebrate life, it also served as an opportunity to stress the importance of bone marrow donations.

Bone marrow is the spongy meshwork material that fills the cavities of large bones. Without functioning bone marrow, a person has no defense against infection and rapidly develops anemia and platelet deficiency.

Bone marrow transplantation is a procedure that holds hope of prolonged survival and cure for patients with various diseases, including leukemia, lymphomas, multiple myeloma, advanced or resistant solid tumors such as in breast cancer, severe aplastic anemia and selected immune deficiency disorders. Approximately 20,000 bone marrow transplants take place annually at more than 300 centers worldwide.

Sanderfeld's donation to Aubree helped her to overcome osteopetrosis -- a rare disease that occurs when the bone marrow does not work properly. Osteopetrosis causes bones to grow inward and become dense instead of growing outward and becoming longer. Had it not been for Sandersfeld's donation, Aubree would not have grown and likely would have died.

Doctors diagnosed Aubree with osteopetrosis when she was 4 months old. The search for a donor then began. Timing was paramount. Aubree had already lost her sight permanently and was likely to loose her hearing soon. A sibling is the most likely donor candidate, but Aubree is an only child. Neither of her parents were matches. The UI Bone Marrow Transplantation Program identified Sandersfeld, who was on a donor registry list, as a match. He gave his initial donation when Aubree was 7 months old. The first marrow did not take, so Sandersfeld donated again when Aubree was 14 months old.

On Oct. 25, thanks to the bone marrow donation, doctors declared Aubree cured of her disease.

"Aubree is here today because a donor was there to donate," Bev Dunn said.

Not only did Sandersfeld give the gift of life to Aubree, he also inspireed Aubree's aunt, Barb Blanc, to register as a bone marrow donor and then later actually to donate. Blanc also attended the reunion.

To find out more about becoming a bone marrow donor, contact the Iowa Marrow Donor Program at University of Iowa Hospitals & Clinics 1-800-944-8220. .