Hypertrophic cardiomyopathy in myosin-binding protein C (MYBPC3) Icelandic founder mutation carriers. Issue 1 (5th April 2020)

• Record Type: Journal Article
• Authors: Adalsteinsdottir, Berglind; Burke, Michael; Maron, Barry J; Danielsen, Ragnar; Lopez, Begoña; Diez, Javier; Jarolim, Petr; Seidman, Jonathan; Seidman, Christine E.; Ho, Carolyn Y; Gunnarsson, Gunnar Th
• Is Part Of: Open heart. Volume 7:Issue 1(2020)
• Publication Date: 2020-04-05
• Subjects: cardiomyopathy hypertrophic -- genetics -- echocardiography; Cardiology -- Periodicals; Heart -- Diseases -- Periodicals; Heart -- Diseases -- Patients -- Periodicals; 616.12005
• DOI: 10.1136/openhrt-2019-001220
• Languages: English
• ISSNs: 2398-595X

Abstract

Abstract : Objective: The myosin-binding protein C ( MYBPC3 ) c.927-2A>G founder mutation accounts for >90% of sarcomeric hypertrophic cardiomyopathy (HCM) in Iceland. This cross-sectional observational study explored the penetrance and phenotypic burden among carriers of this single, prevalent founder mutation. Methods: We studied 60 probands with HCM caused by MYBPC3 c.927-2A>G and 225 first-degree relatives. All participants underwent comprehensive clinical evaluation and relatives were genotyped. Results: Genetic and clinical evaluation of relatives identified 49 genotype-positive (G+) relatives with left ventricular hypertrophy (G+/LVH+), 59 G+without LVH (G+/LVH−) and 117 genotype-negative relatives (unaffected). Compared with HCM probands, G+/LVH+ relatives were older at HCM diagnosis, had less LVH, a less prevalent diastolic dysfunction, fewer ECG abnormalities, lower serum N-terminal pro-B-type natriuretic peptide (NT-proBNP) and high-sensitivity cardiac troponin I levels, and fewer symptoms. The penetrance of HCM was influenced by age and sex; specifically, LVH was present in 39% of G+males but only 9% of G+females under age 40 years (p=0.015), versus 86% and 83%, respectively, after age 60 (p=0.89). G+/LVH− subjects had normal wall thicknesses, diastolic function and NT-proBNP levels, but subtle changes in LV geometry and more ECG abnormalities than their unaffected relatives. Conclusions: Phenotypic expression of the Icelandic MYBPC3 founder mutation varies by age, sex and proband status. Men are more likely to have LVH at a younger age, and disease manifestations were more prominent in probands than in relatives identified via family screening. G+/LVH− individuals had subtle clinical differences from unaffected relatives well into adulthood, indicating subclinical phenotypic expression of the pathogenic mutation.