The Australian girl had a seemingly normal birth in May 2008 but, within hours, she began having multiple seizures -- as many as 10 an hour -- as sulfite build-up began to poison her brain.
But her parents refused to let her die and successfully lobbied Southern Health's Monash Children's Hospital in Melbourne to try an experimental treatment that had only been used on mice.
"There was courage or there was death," the mother, who requested anonymity, told Australia's TV 9 in a telephone link-up. "If she wasn't treated, she would die a very painful death."
With the clock ticking, doctors who treated Baby Z gained approval from the hospital's ethics board and a family court to use the experimental treatment.
Now, doctors consider 18-month-old Baby Z cured and a second child, Baby P of Germany, is successfully undergoing the same therapy.
Schwarz and others who pioneered her startling recovery will appear before the Food and Drug Administration Tuesday looking for a fast-track application for an orphan drug approval in the United States.
But their medical journey raises ethical questions about using untested therapies on children who can't speak for themselves.
"This is not voodoo or snake oil," said Mark Sands, professor of internal medicine and genetics at Washington University School of Medicine in St. Louis, who knows one of the German co-researchers, Jochen Reiss.
"This approach is based on very good science," he said.
About 25 million Americans suffer from orphan diseases, those that affect fewer than 200,000 nationwide.
"A lot of things are very debilitating for a small number of people," said Dr. Timothy Cote, director of orphan drug product development at the FDA. "They are individually infrequent, but collectively common."
Worldwide, there are only about 50 cases of molybdenum cofactor, or sulfite oxidase deficiency, mostly in Europe and in the United States, according to the National Institutes of Health.
Molybdenum, like other organic metals, is essential for the human body. Its cofactor is a small, complicated molecule that acts as a carrier to help the metal interact with proteins and enzymes so they can function properly.
When the cofactor is missing, toxic sulfite builds and begins to cause degeneration of neurons on the brain and eventually death.
"This was the first time I ever saw this," said Dr. Alex Veldman, the Monash pediatrician and neonatologist who headed up Baby Z's treatment. "It's very funny, now I am regarded a world specialist but I can tell you that before last May, I couldn't even spell it."
Baby Z had a healthy birth on May 1, 2008, at a local children's hospital and, at first, doctors didn't realize she lacked the cofactor.
"As long as the baby is in utero, the mom is detoxifying," Veldman told ABCNews.com. "When she was born and the cord is clamped, the detox mechanism is interrupted and the sulfite builds up."