Family history highly predictive of mutations in HCM

see Clinical predictors of genetic testing outcomes in hypertrophic cardiomyopathy

The risk of sudden death in individuals with hypertrophic cardiomyopathy (HCM), particularly young athletes, is alarmingly high. But only about half of patients with a clinical diagnosis ever receive a definitive genetic diagnosis. In a 10-year analysis of Australian HCM patients published in this issue, Ingles and colleagues from three major specialized cardiac genetic clinics in Australia found that a genetic diagnosis is much more likely in patients with a family history of HCM than in those without such a history. Of those with an established family history of HCM, 102 (72%) received a definitive diagnosis, compared with 36 (29%) of patients with no family history. The mutation-detection rate for those with a family history of HCM increased to 89% among individuals with family members who had died suddenly. The authors identified causative mutations in 10 genes, with MYBPC3 and MYH7 accounting for more than 50% of cases. They note that the large difference in mutation-detection rate has direct clinical relevance because patients can be more appropriately counseled regarding their likelihood of receiving a genetic diagnosis based on their family history. The results may also assist in developing an algorithm to assess HCM patients’ risk of heart failure or sudden death. —Karyn Hede, News Editor

High-throughput techniques speed genetic diagnosis of FH

see The use of next-generation sequencing in clinical diagnosis of familial hypercholesterolemia

Despite the high risk of heart disease and early death that comes with inherited high cholesterol levels, three of four people in England carrying familial hypercholesterolemia (FH) gene mutations are unaware they have the disorder. Current genetic testing is costly, and few take advantage of it. A recent yearlong study now reveals that benchtop sequencing of known FH genes has high sensitivity and offers an affordable option for screening patients in a clinical setting. The research team, from Imperial College, London, studied a group of patients referred for genetic screening by a lipid clinic and compared the results with those for a validation group of patients with a known FH molecular diagnosis. The researchers studied two systems: a targeted sequencing protocol and a PCR-based array system with a more limited sequencing capacity. Both methods detected all cases in previously diagnosed patients, with the exception of two cases involving large deletions and duplications that were missed in the PCR-based system. The mutation-detection rates among new patients with definite (66%) and possible (26%) FH were comparable to those reported in published studies. The researchers report that the PCR-based system was much faster—handling 96 samples per day—and less expensive to run, and they suggest that PCR-based screening may be an affordable option for clinical screening of large numbers of patients with suspected FH, allowing more at-risk individuals to be identified and treated. —Karyn Hede, News Editor