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G+P- MYBPC3 Carrier Surveillance — EECC MCQ

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ModerateCardiomyopathyG+P- MYBPC3 Carrier SurveillanceEECC

A 35-year-old man with a family history of HCM undergoes genetic testing and is found to carry a pathogenic MYBPC3 truncating variant. His echocardiogram shows normal wall thickness (MWT 10 mm) and normal LVEF. He is genotype-positive, phenotype-negative. What is the recommended surveillance?

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Correct answer: A — Annual or biennial clinical surveillance with ECG and echocardiography is recommended — MYBPC3 variants have age-dependent penetrance and the hypertrophic phenotype may develop at any age; exercise testing and CMR may be added periodically

Genotype-positive, phenotype-negative (G+P-) individuals carry a pathogenic mutation but have not yet developed the clinical phenotype (LVH). The 2023 ESC Cardiomyopathy Guidelines recommend: (1) regular surveillance with ECG and echocardiography every 1-2 years (annually during adolescence, may extend to 2-5 yearly in adults if stable); (2) MYBPC3 has age-dependent penetrance — the hypertrophic phenotype may appear at any age from childhood to late adulthood (later onset than MYH7 on average); (3) exercise ECG periodically (may reveal exercise-induced arrhythmias or abnormal BP response before overt LVH develops); (4) CMR may be considered (can detect subtle early hypertrophy before echo criteria are met); (5) NO exercise restriction for G+P- individuals (no phenotype = no restriction); (6) genetic counselling for family planning.

Reference: ESC (2023): Cardiomyopathies Guidelines