Cardiac and clinical phenotype in Barth syndrome.
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% +/- 10%, mean fractional shortening of 28% +/- 5%, and mean left ventricular end-diastolic volume z score of 1.9 +/- 1.8. Left ventricular morphology demonstrated increased trabeculations or true noncompaction in 53%. Of 16 patients who were evaluated at > or = 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: < 4000 cells per microL) in 25% of those who were not on granulocyte colony-stimulating factor. Hypocholesterolemia was present in 24%, decreased low-density lipoprotein cholesterol in 56%, low prealbumin in 79%, and mildly elevated creatine kinase in 15%.


CONCLUSIONS
Our cohort demonstrated clinical variability, but most had cardiomyopathy and diminished growth velocity, with a propensity toward neutropenia and low cholesterol. There was increased incidence of ventricular arrhythmia, predominantly in adolescents and young adults. Barth syndrome should be considered when boys present with cardiomyopathy, especially when associated with increased left ventricular trabeculations, neutropenia, skeletal muscle weakness, or family history indicating an X-linked pattern of inheritance.
Spencer
Carolyn T
CT
Congenital Heart Center, University of Florida College of Medicine, PO Box 100296, Gainesville, FL 32610-0296, USA. cspencer@pedcard.ufl.edu
Bryant
Randall M
RM
Day
Jane
J
Gonzalez
Iris L
IL
Colan
Steven D
SD
Thompson
W Reid
WR
Berthy
Julie
J
Redfearn
Sharon P
SP
Byrne
Barry J
BJ
D000217:Acyltransferases; D000293:Adolescent; D000328:Adult; D002311:Cardiomyopathy, Dilated / Q000000981:diagnostic imaging / Q000235:genetics / Q000473:pathology*; D002648:Child; D002675:Child, Preschool; D008078:Cholesterol, LDL / Q000172:deficiency; D015331:Cohort Studies; D003402:Creatine Kinase / Q000097:blood; D003430:Cross-Sectional Studies; D004252:DNA Mutational Analysis; D004392:Dwarfism / Q000235:genetics / Q000473:pathology; D004452:Echocardiography; D004562:Electrocardiography; D040181:Genetic Diseases, X-Linked / Q000000981:diagnostic imaging / Q000235:genetics / Q000473:pathology*; D005838:Genotype; D016179:Granulocyte Colony-Stimulating Factor / Q000627:therapeutic use; D018737:Hand Strength; D006352:Heart Ventricles / Q000473:pathology; D006801:Humans; D007223:Infant; D007970:Leukopenia / Q000188:drug therapy / Q000235:genetics; D008297:Male; D018908:Muscle Weakness / Q000235:genetics / Q000473:pathology; D010641:Phenotype; D011228:Prealbumin / Q000172:deficiency; D011506:Proteins / Q000235:genetics; D013318:Stroke Volume; D013577:Syndrome; D014157:Transcription Factors / Q000172:deficiency / Q000235:genetics
D008078:Cholesterol, LDL; D011228:Prealbumin; D011506:Proteins; D014157:Transcription Factors; D016179:Granulocyte Colony-Stimulating Factor; D000217:Acyltransferases; C108675:TAFAZZIN protein, human; D003402:Creatine Kinase