A Nationwide Study on Hypertrophic Cardiomyopathy in Iceland: Evidence of a MYBPC3 Founder Mutation
Background—The geographic isolation and homogeneous population of Iceland is ideally suited to ascertain clinical and genetic characteristics of hypertrophic cardiomyopathy (HCM) at the population level.
Methods and Results—Medical records and cardiac imaging studies obtained between 1997 and 2010 were reviewed to identify Icelandic patients with HCM. Surviving patients were recruited for clinical and genetic studies. A previously identified Icelandic mutation, MYBPC3 c.927-2A>G, was genotyped, and mutation-negative samples were sequenced for HCM genes and other hypertrophic genes. Record review identified 180 HCM patients. Genetic analyses of 151 patients defined pathogenic mutations in 101 (67%), including MYBPC3 c.927-2A>G (88 patients; 58%), 4 other MYBPC3 or MYH7 mutations (5 patients; 3.3%), and 2 GLA mutations (8 patients; 5.3%). Haplotype and genetic genealogical data defined MYBPC3 c.927-2A>G as a founder mutation, introduced into the Icelandic population in the 15th century, with a current population prevalence of 0.36%. MYBPC3 c.927-2A>G mutation carriers exhibited phenotypic diversity but were younger at diagnosis (42 vs. 49 years, p=0.001) and sustained more adverse events (15% vs. 2%, p=0.02) than mutation-negative patients. All-cause mortality for HCM patients was similar to an age-matched Icelandic population (Hazard Ratio 0.98, p=0.9). HCM-related mortality (0.78%/year) occurred at a mean age of 68 compared to 81 years for non-HCM related mortality (p=0.02).
Conclusions—A founder MYBPC3 mutation that arose over 550 years ago is the predominant cause of HCM in Iceland. The MYBPC3 c.927-2A>G mutation is associated with low adverse event rates but earlier cardiovascular mortality, illustrating the impact of genotype on outcomes in HCM.
- Received May 17, 2014.
- Revision received July 10, 2014.
- Accepted July 15, 2014.