ABSTRACT
OBJECTIVES: The purpose of this study was to describe the clinical and molecular features of a large family with maternally inherited cardiomyopathy (MICM). BACKGROUND: Recently, several mitochondrial deoxyribonucleic acid (mtDNA) point mutations have been associated with MICM. However, the distinctive clinical and morphologic features of MICM are not fully appreciated. This is partially due to the small size of the reported pedigrees, often lacking detailed clinical and laboratory information. METHODS: Clinical and genetic analysis of the family was carried out. RESULTS: Echocardiography showed mostly symmetrical hypertrophic cardiomyopathy in 10 family members. The illness had an unfavorable course. Progressive heart failure occurred in three subjects, who eventually died; one individual underwent heart transplantation. Electrocardiographic or echocardiographic signs of cardiac hypertrophy in the absence of significant clinical complaints were observed in five subjects. Neurologic examination was normal. The mutation was detected in blood from all available subjects. Abundance of mutated molecules ranged between 13% and 100% of total mtDNA genomes. The severity of the disease could not be foreseen by the proportion of mutation in blood. CONCLUSIONS: This report contributes a better description of the clinical aspects of MICM and provides important clues to distinguish it from hypertrophic cardiomyopathy. We suggest that mtDNA mutations, particularly in the transfer ribonucleic acid for isoleucin, should be systematically searched in patients with MICM. The identification of an underlying maternally inherited mitochondrial DNA defect in familial cases of cardiomyopathy may considerably influence the management and genetic counseling of affected patients.
Subject(s)
Cardiomyopathy, Hypertrophic/genetics , DNA, Mitochondrial/genetics , Genetic Predisposition to Disease/genetics , Point Mutation/genetics , Sex Chromosome Aberrations/genetics , X Chromosome , Adolescent , Adult , Aged , Aged, 80 and over , Cardiomyopathy, Hypertrophic/diagnosis , Child , Child, Preschool , DNA Mutational Analysis , Female , Heart Failure/diagnosis , Heart Failure/genetics , Humans , Male , Middle Aged , Pedigree , Phenotype , Polymorphism, Restriction Fragment Length , Pregnancy , RNA, Transfer, Ile/geneticsABSTRACT
A novel mtDNA mutation at position nt. 4300 in the tRNAIle gene is associated with hypertrophic cardiomyopathy inherited as a maternal trait. Interestingly, this mutation seems to cause a pure heart disease as opposed to most other mtDNA mutations, which are associated with multisystemic disorders. Hypertrophic cardiomyopathies are genetically heterogeneous, and mtDNA defects should be considered in the differential diagnosis, especially when there is evidence of maternal inheritance.
