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Unlabelled: Barth syndrome is an X-linked disorder usually diagnosed in infancy. It is characterized by hypotonia, dilated cardiomyopathy, neutropenia, growth retardation, and 3-methylglutaconic aciduria. The syndrome is typically caused by mutations in the TAZ (G4.5) gene, which encodes a novel protein family called the tafazzins. We report the case of two brothers with Barth syndrome and left ventricular noncompaction (LVNC) caused by a splice donor mutation in TAZ. Both had impaired sucking ability at the age of 2 months. The elder brother was diagnosed with LVNC at the age of 4 months; by that time he had developed severe heart failure with metabolic decompensation. He died at 12 months of age due to intractable heart failure despite pharmacological therapy with diuretics, an angiotensin-converting enzyme inhibitor, and a beta-blocker. However, the younger brother, who was diagnosed as having Barth syndrome and LVNC with heart failure at the age of 2 months, received early medical treatment and demonstrated normal echocardiographic findings., Conclusion: The clinical courses of Barth syndrome observed in our cases show the phonotypic variability of this syndrome and suggest that early therapy may be beneficial for maintaining cardiac function.

TAZ (G4.5) was initially identified as the gene associated with Barth syndrome and left ventricular noncompaction (LVNC). The purpose of this study was to investigate patients with LVNC for disease-causing mutations in TAZ. In 124 Japanese patients, including 50 families, mutation analysis of TAZ was performed using DNA sequencing. A splice donor mutation was identified in two brothers with Barth syndrome and LVNC, and a sister who was asymptomatic. However, the variant was not identified in either parent or the maternal grandparents, all of whom were asymptomatic. Due to the recurrent inheritance of this variant by each of the children we concluded that this was evidence of gonadal mosaicism in the obligate carrier mother, the first reported occurrence of this in Barth syndrome.