Family Says Precision Medicine Provided New Hope for Sick Daughter

— -- The family of a toddler who lost the ability to walk credits a new, cutting-edge medical approach with her remarkable recovery.

The toddler, Cara Greene, was 15 months old when her parents, Kristen and Clayton Greene, said they began noticing alarming changes in her otherwise accelerated development.

“She first started just being unsteady with walking [and] slowly over time we noticed that her arms became weak,” Kristen told ABC News. “She got to the point where she was so unsteady walking and fell so often that she actually stopped walking.”

The Greenes, of Wilmington, North Carolina, said they sought the advice of many doctors but none had an answer. Some suggested a possible autoimmune disorder.

“No matter how much we did, no matter how much we tried to help her, there wasn’t anything that we could do to stop her from getting worse,” Kristen said.

In search of more help, the Greenes turned to precision medicine, which focuses on an individual patient’s DNA to map a diagnosis and a potential cure. The Precision Medicine Initiative was started by President Obama last year to pursue the development of therapies targeted to each patient's genes, environment and lifestyle.

“We're looking at a person, their genetic makeup, the environmental triggers in their life, and their lifestyle,” Dr. Arefa Cassoobhoy, medical editor of WebMD, told ABC News' Robin Roberts. "And we're looking to that to focus therapy.”

Dr. David Goldstein, director of the Institute for Genomic Medicine at Columbia University, was doing groundbreaking work with gene sequencing when he took on Cara’s case. His team collected blood samples from Cara and both of her parents to find an answer to her medical mystery.

“When a child comes into the clinic and they have something seriously wrong we can take a blood sample and we can almost immediately generate that individual’s complete genome,” Goldstein said. “Then we can look through it and try to find the cause of disease.”

Through genetic sequencing, which is the cornerstone of precision medicine, doctors discovered that Kristen and Clayton Greene both carried a gene mutation that affected Cara’s ability to produce a protein, thus resulting in a severe vitamin B12 deficiency.

The only treatment necessary for Cara was to take a high dose of vitamin B12 in the form of an oral supplement. Within weeks, Cara began to improve.

“Cara's doing phenomenal today,” Kristen said of her daughter, who is now 3 years old. “Dr. Goldstein and his team, we credit him for saving Cara's life. She's getting to be a kid and make up for lost time.”

For more information on precision medicine and other medical innovations, watch "Path to a Breakthrough," a five-part original video series developed in partnership with WebMD and Robin Roberts and her independent production company, Rock’n Robin Productions.