Mutations in alpha-tropomyosin are a rare cause of familial hypertrophic cardiomyopathy, accounting for approximately 3 percent of cases. Mutations in cardiac troponin T account for approximately 15 percent of cases of familial hypertrophic cardiomyopathy in this referral-center population. These mutations are characterized by relatively mild and sometimes subclinical hypertrophy but a high incidence of sudden death. Genetic testing may therefore be especially important in this group.

Three novel 63 cardiac myosin heavy chain (MHC) gene missense mutations, Phe513Cys, Gly716Arg, and Arg719Trp, which cause familial hypertrophic cardiomyopathy (FHC) are described. One mutation in exon 15 (Phe513Cys) does not alter the charge of the encoded amino acid, and affected family members have a near normal life expectancy. The Gly716Arg mutation (exon 19; charge change of +1) causes FHC in three family members, one of whom underwent transplantation for heart failure. The Arg719Trp mutation (exon 19; charge change of -1) was found in four unrelated FHC families with a high incidence of premature death and an average life expectancy in affected individuals of 38 yr. A comparable high frequency of disease-related deaths in four families with the Arg719Trp mutation suggests that this specific gene defect directly accounts for the observed malignant phenotype. Further, the significantly different life expectancies associated with the Arg719Trp vs. Phe513Cys mutation (P < 0.001) support the hypothesis that mutations which alter the charge of the encoded amino acid affect survival more significantly than those that produce a conservative amino acid change. (J. Clin. Invest. 1994. 93:280-285.)

Severe left ventricular dysfunction with associated conduction disturbances and ventricular arrhythmias occur in patients with terminal stage cardiac Fabry disease. Furthermore, LVH is present and associated with thinning of the base of the left ventricular posterior wall. In contrast to typical Fabry disease, accumulation of glycosphingolipids was observed in myocardial cells but not in other organs.

The clinical features of cardiac involvement in mitochondrial diseases vary in the different subgroups of these disorders. Particular mitochondrial mutations can cause characteristic cardiac abnormalities.

Population-based screening for heart disease in this age range is limited by various factors. To analyze the mechanisms of sudden death in adolescents, we, therefore, are in need of a nationwide registry that includes autopsies for all deadly events.

Background —Mutations that cause familial hypertrophic cardiomyopathy have been identified in several genes that encode contractile proteins. Patients with mutations in the cardiac troponin T (cTnT) gene have particularly poor prognosis but only mild hypertrophy. To date, no benign mutation in the cTnT gene has been reported. The clinical characteristics and prognosis of patients with the Phe110Ile mutation in the cTnT gene is unclear because few affected individuals have been identified. Methods and Results —Forty-six probands with familial hypertrophic cardiomyopathy were screened for mutations in the cTnT gene. The Phe110Ile missense mutation was found in 6 probands. Individuals in the 6 families were analyzed genetically and clinically. Haplotype analysis was performed with markers encompassing the cTnT gene. Left ventricular hypertrophy was classified as type I, II, III, or IV according to the criteria of Maron et al. The Phe110Ile mutation in the cTnT gene was identified in 16 individuals. Two of the 6 families shared the same flanking haplotype, and 4 were different from each other. Affected individuals exhibited different cardiac morphologies: 4 had type II, 6 had type III, and 3 had type IV hypertrophy with apical involvement. Three individuals with the disease-causing mutation did not fulfill clinical criteria for the disease. The product-limit survival curve analysis demonstrated a favorable prognosis. Conclusions —Multiple independent mutations of residue 340 in the cTnT gene have been described, suggesting that this may be a “hot spot” for such events. The Phe110Ile substitution causes hypertrophic cardiomyopathy with variable cardiac morphologies and a favorable prognosis.

De novo mutations in the alpha-tropomyosin gene can result in hypertrophic cardiomyopathy that may appear to be sporadic but in subsequent generations gives rise to familial disease. Individuals with sporadic hypertrophic cardiomyopathy should be advised of the risk of transmission to offspring. In addition, these findings provide the strongest genetic evidence that mutations in the alpha-tropomyosin gene are directly responsible for hypertrophic cardiomyopathy.

These results demonstrate that HCM with sarcomere gene mutations can be associated with increased cardiovascular events compared with HHD or HCM without sarcomere gene mutations.