Cardiac and clinical phenotype in Barth syndrome.(Author abstract)

OBJECTIVE. Barth syndrome, an X-linked disorder that is characterized by cardiomyopathy, neutropenia, skeletal myopathy, and growth delay, is caused by mutations in the taffazin gene at Xq28 that result in cardiolipin deficiency and abnormal mitochondria. The clinical phenotype in Barth syndrome has not been characterized systematically, and the condition may be underrecognized. We sought to evaluate extent of cardioskeletal myopathy, potential for arrhythmia, delays in growth, and biochemical correlates of disease severity in patients with this disorder. METHODS. We conducted an observational, cross-sectional study of the largest cohort of patients with Barth syndrome to date (n = 34; age range: 1.2-22.6 years). Evaluation included echocardiography, electrocardiography (standard and signal-averaged), microvolt T wave alternans analysis, biochemical and hematologic laboratory analyses, and physical therapy evaluation of skeletal myopathy. RESULTS. Family history was positive for confirmed or suspected Barth syndrome in 63%. Ninety percent of patients had a clinical history of cardiomyopathy (mean age at diagnosis of cardiomyopathy: 5.5 months; at genetic confirmation of Barth syndrome: 4.6 years). Echocardiography revealed a mean ejection fraction of 50% [+ or -] 10%, mean fractional shortening of 28% [+ or -] 5%, and mean left ventricular end-diastolic volume z score of 1.9 [+ or -] 1.8. Left ventricular morphology demonstrated increased trabeculations or true noncompaction in 53%. Of 16 patients who were evaluated at [greater than or equal to] 11 years of age, 7 (43%) had documented ventricular arrhythmia. Growth deficiency was present (mean weight percentile: 15 %; mean height percentile: 8%). Laboratory analysis revealed low total white blood cell count (absolute count: