Barth syndrome presents in infancy with hypotonia, dilated cardiomyopathy, and neutropenia. We report a patient whose family history included two males who had died suddenly at the age of 15 days and 2 years, respectively. The index case presented with acute metabolic decompensation at 13 days of age. Within 8 h of presenting with metabolic acidosis (pH 7.13), lactic acidemia (18.5 mmol/l), hyperammonemia (375 microg/dl), hypoglycemia (25 mg/dl), and coagulopathy, the patient developed respiratory failure and required intubation. The diagnosis was established by the presence of left ventricular noncompaction and molecular analysis (c.C153G or Y51X mutation of the TAZ gene). The gene product, taffazin, is a homologue of the glycerolipid transferases involved in the phospholipid metabolism as tetralinoleoyl-cardiolipin, a component of the mitochondrial inner membrane. In conclusion, mutations in taffazin impair mitochondrial respiratory chain complexes, which may results in the acute metabolic decompensation and sudden death; cardiac transplantation is the only possibility at the present time.