They are the genetic equivalent of unicorns: 13 adults with genes for rare disorders that always strike in childhood, yet who never developed the disease. The genes are not for complex diseases, such as cancer where DNA variants merely raise the risk of developing a disease; these mutations cause the disease — cystic fibrosis or familial dysautonomia, for example — as surely as 22 makes you go bust in blackjack. Or so everyone thought.
But a new study, published Monday in Nature Biotechnology, challenges that notion. Researchers searched genetic data from nearly 600,000 people in scientific studies or databases of DNA testing company 23andMe, looking for mutations in any of 874 genes known to cause one of 584 severe childhood disorders. The scientists identified 13 people with a mutation that should have made them very, very sick — or dead. Yet here they were, healthy adults.