A retrospective epidemiological and etiological study of metabolic disorders in children with cardiomyopathies.

Cardiomyopathies may be idiopathic or secondary to an underlying definable systemic disorder, especially in a young population. A number of inherited metabolic disorders will lead to hypertrophic or dilated cardiomyopathy. Identifying the metabolic etiologies of cardiomyopathy is important for genetic counseling and identification of appropriate therapeutic interventions. Fifty-eight children aged from 1 to 18 years were diagnosed as suffering from cardiomyopathy over six years. Cardiomyopathies (dilated, hypertrophic or restrictive) were confirmed by echocardiography together with extensive clinical and metabolic investigations. The patients could be divided into two groups, etiology known (50.0%) and idiopathic (50.0%). Among the definable underlying diseases, 31.0% were diagnosed as inherited metabolic disorders, including mitochondrial disorders (n=4), primary systemic carnitine deficiency (n=1), Pompe disease (n=3) and mucopolysaccharidosis (MPS) I (n=1). In this study, there was a large component of idiopathic cardiomyopathies (50.0%), and it is likely that a proportion of these "unknowns" have a diagnosable disorder. Therefore, for cardiomyopathies in children, after exclusion of non-genetic causes, genetic studies and metabolic screening, such as tandem mass spectrometry, urine gas chromatography/mass spectrometry, carnitine level and mitochondrial DNA screening, are recommended.