"We're so excited for her future," says Kristen Greene
Kristen and Clayton Greene quickly went from having a healthy baby daughter to not knowing whether their little girl would live to celebrate her second birthday.
At 15 months old, Cara lost her ability to walk, her arms became limp and her grip was too weak to hold on to anything.
“We had no idea what was wrong,” Kristen, 32, from Wilmington, North Carolina, tells PEOPLE. “It was horrific.”
Medical experts had trouble diagnosing Cara, and each trip to the doctor just led to more questions as to what was the cause of Cara’s symptoms.
“She was just getting sicker and sicker,” she says. “My husband was holding her and he remembers thinking that one day she’ll be in his arms and she won’t be alive.”
But the devoted parents never gave up hope and decided to give precision medicine a shot with the help one of determined doctor.
Dr. David Goldstein, director of the Institute of Genomic Medicine at Columbia University, was working on gene sequencing and took on Cara’s case.
“We got this phone call that they had the results, but we had to wait an entire weekend to find out what they were,” says Kristen. “It was torture. We thought they were going to say she was going to die, so we spent the weekend grieving.”
But what they thought would be a death sentence ended up being a miracle.
Dr. Goldstein told them that they not only had an answer to her health’s steep decline – they also had a simple cure.
“He told us they can rarely give parents good news,” she says. “And on top of that, we could help her.”
Doctors discovered from the genetic sequencing that Kristen and Clayton, 31, both carried a gene mutation that affected Cara’s ability to produce a protein, resulting in a severe vitamin B2 deficiency.
Her condition, Brown-Vialetto-Van Laere syndrome, a rare, neurodegenerative motor neuron disorder, only has approximately 70 known cases worldwide.
With a simple treatment of a high dose of vitamin B12 in the form of an oral supplement, Cara, who turns 4 on August 18, quickly began to improve.
“We are so lucky,” says Kristen. “It makes you realize a lot. We celebrate milestones that other families might not because we know how precious life is.”
Dr. Hansa Bhargava, medical editor and WebMD’s expert pediatrician, tells PEOPLE that a full genetic analysis was very expensive a few years ago, but it now costs significantly less and will only continue to become more affordable.
“The fact that they were able to catch this has a made a huge impact on her life and the life of her parents,” she says. “In progressive diseases, things just continue to get worse.”
The Greenes, who also have a 2-year-old daughter, Susan, say that Cara is making up for the time she lost.
“She can walk again on her own,” she says.
On Tuesday, the family flew to New York City – the first time Cara has been on an airplane or in a hotel – where they stopped by the American Girl store, Dylan’s Candy Bar and saw Aladdin on Broadway.
“Seeing her enjoy life is amazing,” she says. “We’re very lucky. We won’t waste a day.”