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Sarcomeric Genetics of HCM — EECC MCQ

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EasyCardiomyopathySarcomeric Genetics of HCMEECC

A 30-year-old man with HCM (MWT 20 mm, no LVOT obstruction) asks about the genetic basis of his condition. Genetic testing reveals a pathogenic variant in MYH7 (beta-myosin heavy chain). What proportion of HCM is caused by sarcomeric gene mutations?

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Correct answer: D — Approximately 40-60% of HCM is caused by sarcomeric gene mutations, with MYH7 and MYBPC3 accounting for the majority; genotype-negative HCM may represent other aetiologies or undiscovered genetic causes

HCM is the most common inherited cardiomyopathy, with approximately 40-60% of cases having identifiable sarcomeric gene mutations. The most commonly affected genes are: MYH7 (beta-myosin heavy chain, ~20-30%) and MYBPC3 (myosin-binding protein C, ~20-30%), together accounting for 70-80% of genotype-positive cases. Other sarcomeric genes (TNNT2, TNNI3, TPM1, ACTC1, MYL2, MYL3) account for the remainder. The 2023 ESC Cardiomyopathy Guidelines recommend genetic testing for: (1) all patients with a clinical diagnosis of HCM (to enable cascade screening); (2) differentiation from phenocopies (Fabry, Danon, PRKAG2, amyloidosis, Noonan syndrome). Genotype-negative patients should be investigated for non-sarcomeric causes before concluding 'idiopathic' HCM.

Reference: ESC (2023): Guidelines on Cardiomyopathies