The New York Times, May 21, 2018
James Priest couldn’t make sense of it. He was examining the DNA of a desperately ill baby, searching for a genetic mutation that threatened to stop her heart. But the results looked as if they had come from two different infants.
“I was just flabbergasted,” said Dr. Priest, a pediatric cardiologist at Stanford University.
The baby, it turned out, carried a mixture of genetically distinct cells, a condition known as mosaicism. Some of her cells carried the deadly mutation, but others did not. They could have belonged to a healthy child.