The pregnant daughter gave birth to a baby girl, unaware of her father’s diagnosis and the risk that she and her newborn had of developing Huntington’s. Four months later, one of her father’s doctors accidentally let slip her father’s condition, which had been confirmed by genetic testing a month before she gave birth. She got tested and the results came back positive—she had Huntington’s disease.

In a lawsuit issued in 2013, the daughter—whom the suit refers to as “ABC,” because of privacy concerns for her young child—claims that her father’s doctors had a duty to inform her of her father’s diagnosis regardless of his wishes. Had she known she had Huntington’s, ABC says, she would have terminated her pregnancy rather than have a child who was at high risk of both having a life-destroying disease and being raised by a terminally ill single parent.

A lower court threw out the case. But in May 2017, the U.K. Court of Appeal overturned the decision. ABC’s claims, it said, are arguable. That decision may have set an important precedent—that genetic testing extends the duty of a health-care professional beyond the patient. But extending that duty also risks damaging the underlying trust between doctor and patient.

If, as expected, the case goes to trial in 2019, the court will have to decide whether ABC was owed a “duty of care” by her father’s doctors even though she had never been their patient or at any of the facilities at which her father was treated. More broadly, the court will ask if the genetically inheritable characteristic of a condition like Huntington’s disease means that a parent’s confidential diagnosis belongs to the child as well. With further advances in genetic testing, claims to a relative’s genetic information may become increasingly difficult to deny. As one scholar has put it, it will be more common for the relative of a patient to demand access to the patient’s record by declaring—with more than a hint of truth—“I have a claim, because it is about me.”

Over the past 30 years, Heidi Pate has had seven surgeries on her neck. During the first two alone she had 108 lymph nodes removed. She is constantly trying to keep ahead of her cancer and so has allowed surgeons to open her up and move or remove everything that they think could kill her. When they took out her parotid salivary gland at age 32, her face would have been “sucked in and concave” had her surgeon not replaced the gland with muscle taken from the left side of her neck. “I guess my doctor felt sorry for me,” she tells me when I visit her home in Orange Park, Florida.

Heidi’s battle with cancer didn’t begin with her own condition. It began with her mother, Marianne New, who was treated for medullary thyroid carcinoma, known as MTC, in 1987. Marianne had a couple surgeries and recovered fully. But three years later, her daughter started having symptoms of what doctors mistakenly thought was stomach cancer. Just before Heidi’s gallbladder was removed, an intern found swollen lymph nodes in the right side of her neck. Eight weeks later her surgeon did a biopsy and, when the results came back, said: “Yep, that’s thyroid cancer.”