Phenotype is king, researchers say, after 20 family members have condition misdiagnosed

More than 20 members of a family wrongly had a lethal heart rhythm condition diagnosed after incorrect application and interpretation of genetic tests, investigators have reported in a study published in Mayo Clinic Proceedings.1 They say that this demonstrates the hazards of genetic testing when used inappropriately and interpreted incorrectly.

The case involved a Hispanic family whose son had died suddenly in his sleep at age 13. At autopsy the boy’s heart was found to be enlarged and had several abnormalities including fibrillar disarray in the left ventricle, diffuse areas of fibrosis in the papillary muscles, and marked endocardial fibrosis in the left atrium, but the medical examiner deemed the autopsy inconclusive for a specific cardiomyopathy.

After the boy’s death his parents and brother underwent cardiological testing and were initially found to be normal. …