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Hypertrophic cardiomyopathy: an update.

Hypertrophic cardiomyopathy (HCM) is defined as an idiopathic heart muscle disorder which characterised by the presence of left and/or right ventricular hypertrophy in the absence of a systemic or cardiac cause. At post mortem examination the characteristic histology shows myocyte disarray surrounding areas of increased loose connective tissue. The spectrum of disease is wider than the phenotype which relies on the diagnostic presence of unexplained left ventricular hypertrophy. During the past 5 years, one of the genes which causes HCM has been discovered, several additional loci have been identified, disease causing mutations are being introduced into transgenic animals and functional studies of disease muscle have revealed abnormalities in the sarcomere function. RNase protection and various other methods can be used to screen an individual HCM patient for myosin mutations. To date 17 missense mutations have been identified. They have only been found in individuals affected with hypertrophic cardiomyopathy and they have not been detected in unaffected relatives or in over 200 other unrelated individuals. We have screened the beta cardiac myosin heavy chain gene in individuals with sporadic hypertrophic cardiomyopathy. In 2 of 7 probands who had typical clinical features of HCM, but unaffected parents, de novo missense mutations were identified (Arg723Cys and Glu924Lys). In one of the probands the disease was passed on in the germline to her daughter. De novo mutations, then, can cause both the familial and sporadic forms of hypertrophic cardiomyopathy. This indicates that sporadic and familial hypertrophic cardiomyopathy represent different parts of the spectrum of the same condition and this has important implications for management in relation to genetic counseling and risk factor stratification.(ABSTRACT TRUNCATED AT 250 WORDS)