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Counselling issues in familial hypertrophic cardiomyopathy
1Department of Molecular and Clinical Genetics, Royal Prince Alfred Hospital, Sydney, NSW, Australia.
Insights
Familial hypertrophic cardiomyopathy (FHC) shows variable clinical presentations and progression rates. Different genetic defects, like missense mutations versus protein truncating mutations, influence FHC penetrance and sudden cardiac death risk.
Area of Science:
- Cardiology
- Genetics
- Molecular Biology
Background:
- Familial hypertrophic cardiomyopathy (FHC) is a genetic disorder characterized by left ventricular hypertrophy.
- Clinical presentations and disease progression in FHC are highly variable.
- Understanding genotype-phenotype correlations is crucial for managing FHC.
Purpose of the Study:
- To compare phenotypes and genotypes in three FHC families with distinct genetic defects.
- To illustrate the variable clinical presentations and progression rates in FHC.
- To investigate the impact of different mutation types on FHC penetrance.
Main Methods:
- Comparative analysis of phenotypes and genotypes across three FHC families.
- Identification of specific genetic mutations: Gln969X (protein truncating) and Asn755Lys (missense) in the cardiac myosin binding protein C gene.
- Identification of a missense mutation (Arg453Cys) in the cardiac beta myosin heavy chain gene.
Main Results:
- Protein truncating mutation (Gln969X) showed 27% penetrance (ages 0-40 years).
- Missense mutations in the same gene exhibited significantly higher penetrance (93% ages 0-40 years).
- Variable penetrance and unpredictable sudden cardiac death risk complicate FHC diagnosis and management.
Conclusions:
- Genetic defects in FHC significantly influence disease penetrance and clinical outcomes.
- Missense mutations are associated with higher penetrance compared to protein truncating mutations in FHC.
- The variability in FHC necessitates tailored genetic counseling and clinical management strategies.
Abstract:
To illustrate the variable clinical presentations and rates of progression in familial hypertrophic cardiomyopathy (FHC), phenotypes and genotypes were compared in three FHC families with different genetic defects. In the first family, the FHC abnormality was a protein truncating mutation (Gln969X) in the cardiac myosin binding protein C gene. The second family had a missense change (Asn755Lys) in the same gene. A missense mutation (Arg453Cys) in the cardiac beta myosin heavy chain gene was present in the third family. Penetrance associated with the Gln969X defect was 27% in the age range 0 to 40 years. This was considerably less than the 93% penetrance (0 to 40 years) observed in the two families with missense mutations. The variable penetrance in FHC, as well as the unpredictability of sudden cardiac death, complicates clinical diagnosis and management, including genetic counselling. Although a genetic disease with a predominantly adult onset, there are counselling issues in FHC which set it aside from other adult onset disorders.
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