Isolated noncompaction of the ventricular myocardium (INVM, MIM 300183 and 
604169) is a congenital unclassified cardiomyopathy with numerous prominent 
trabeculations and deep intertrabecular recesses in a hypertrophied and 
hypokinetic myocardium. Mutations in the G4.5 gene result in a wide spectrum of 
severe infantile X-linked cardiomyopathic phenotypes including Barth syndrome 
with dilated cardiomyopathy and INVM. Molecular genetic analysis of INVM has 
only been performed in pediatric patients. Although adult INVM patients show 
similar cardiac abnormalities, the influence of genetic factors, especially of 
mutations in G4.5, is unknown. We analyzed 25 adult INVM patients for the 
presence of mutations in the G4.5 gene and performed a pedigree analysis of 
probands. Mutations were not found in the coding sequence or splice sites of 
G4.5. Systematic analysis of relatives from seven of nine probands showed 
multiple affected members consistent with an autosomal dominant pattern of 
inheritance in the majority of cases. We conclude that INVM in the adult is an 
autosomal dominant disorder rarely caused by mutations in G4.5 and therefore 
genetically distinct from infantile X-linked cases.