Thirteen people in the world have been named “genetic superheroes” because they have remained healthy despite carrying genetic mutations that usually lead to childhood diseases. Doctors say they could provide life-saving treatments for many serious diseases, but there’s a catch.

The problem: Doctors don’t know why they are and can’t find them because they were identified by scientists during a study of more than a half-million people’s DNA — but the researchers only had access to their genes, not the identities of the people themselves, The Independent reports.

Each of the 13 should have been susceptible to such disorders as cystic fibrosis, which begin in early childhood as the result of a defect in a gene, but they are apparently completely unaffected by their problem genes.

If they can be identified, these individuals might help lead researchers to discover the naturally occurring mechanisms that have kept the conditions at bay and design new treatments.

The people were part of the Resilience Project, which examined 589,000 genetic codes in an attempt to find people who are immune to the genetic variants that usually lead to diseases.

"Most genomic studies focus on finding the cause of a disease, but we see tremendous opportunity in figuring out what keeps people healthy,” Resilience Project co-founder Eric Schadt, from the Icahn School of Medicine at Mount Sinai, New York City, said. “Millions of years of evolution have produced far more protective mechanisms than we currently understand.

“Characterizing the intricacies of our genomes will ultimately reveal elements that could promote health in ways we haven't even imagined."