Genetic Testing Challenges in Precision Medicine: Inadequate Relay of Test Limits Delays Diagnosis
January 27, 2026
A Cascade Testing Failure Traced to a Buried Limitation
An oncologist referred a 76-year-old woman with breast cancer for genetic counseling after learning about her family’s cancer history. Her son had been diagnosed with kidney cancer. A large multi-gene panel had identified a pathogenic variant in his ATM gene, putting him and his blood relatives at elevated cancer risk. After confirming the same variant in the mother, her genetic counselor recommended that her younger son also undergo cascade testing.
The younger son’s internal medicine provider ordered a 32-gene panel from a different laboratory and flagged the familial ATM variant in the order. The lab ran the panel knowing it could not detect that specific variant. It noted the limitation only as an “additional comment” buried in the report’s clinical interpretation section. The physician told the younger son he tested negative for the familial variant. In fact, he carried it.
After the younger son died unexpectedly, his 20-year-old daughter began losing her balance and her ability to speak. The grandmother mentioned her granddaughter’s symptoms to her own genetic counselor, who reviewed the younger son’s original test report and spotted the buried limitation language.
Doctors evaluated the granddaughter and diagnosed her with ataxia-telangiectasia — a rare, progressive neurological disorder that develops when a patient inherits two copies of a pathogenic ATM variant. Clearer communication from the lab about what its test could not detect might have led to this diagnosis a year sooner.
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