Searching for Similar Diagnosis Through DNA

By AMY HARMON
New York Times

The girls had never met, but they looked like sisters.

There was no missing the similarities: the flat bridge of their noses, the thin lips, the fold near the corner of their eyes. And to the families of 14-year-old Samantha Napier and 4-year-old Taygen Lane there was something else, too. In the likeness was lurking an explanation for the learning difficulties, the digestion problems, the head-banging that had troubled each of them, for so long.

Several of the adults wiped tears from their eyes. “It’s like meeting family,” said Jessica Houk, Samantha’s older sister, who accompanied her and their mother to a Kentucky amusement park last July to greet Taygen.

But the two families are not related, and would never have met save for an unusual bond: a few months earlier, a newly available DNA test revealed that Samantha and Taygen share an identical nick in the short arm of their 16th chromosomes.

With technology that can now scan each of an individual’s 46 chromosomes for minute aberrations, doctors are providing thousands of children lumped together as “autistic” or “developmentally delayed” with distinct genetic diagnoses. The symptoms, they are finding, can be traced to one of dozens of deletions or duplications of DNA that were previously hard or impossible to detect.

Some mutations are so rare that they are known only by their chromosomal address: Samantha and Taygen are two of only six children with the diagnosis “16p11.2.”

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