Molecular and Clinical Aspects of Inherited Cardiomyopathies

Abstract

Hypertrophic cardiomyopathy (HCM) is phenotypically and genotypically a heterogeneous disease. Since 1989, four chromosomal loci have been identified for HCM and the genes residing on three of these have been identified as β-myosin heavy chain (β-MHC), cardiac troponin-T and α-tropomyosin. These genes code for sarcomere proteins and exhibit the same phenotype, suggesting that HCM is a disease of the sarcomere. Over 40 missense mutations and one deletion of the β-MHC gene have been identified. Similarly, missense mutations in the α-tropomyosin gene and the cardiac troponin-T gene have been identified. From genetic studies, including de novo mutations, it is established that these mutations are indeed responsible for HCM. The molecular basis of the pathogenesis of the cardiac hypertrophy appears to be a compensatory response to the primary defect. In addition to providing a definitive presymptomatic diagnosis, studies correlating β-MHC mutations with clinical prognosis suggest they have significant predictive value and can be helpful in genetic counselling and medical management.

Dilated cardiomiopathies (DCM), the most common form of cardiomyopathies, have an estimated prevalence of nearly 40 per 100000 individuals, and are the most common cause for cardiac transplantation in the United States. Familial dilated cardiomyopathy is thought to account for approximately 20% of the so-called cases of idiopathic DCM.

Key Words:

• hypertrophic cardiomyopathy
• β-myosin heavy chain
• cardiac troponin T
• α-tropomyosin