Barth syndrome (BTHS) is an X-linked recessive disease primarily affecting 
males. Clinically, the disease is characterized by hypertrophic or dilated 
cardiomyopathy, skeletal myopathy, chronic/cyclic neutropenia, 
3-methylglutaconic aciduria, growth retardation and respiratory chain 
dysfunction. It is caused by mutations in the TAZ gene coding for the tafazzin 
protein which is responsible for cardiolipin remodeling. In this work, we 
present a novel pathogenic TAZ mutation c.83T>A, p.Val28Glu, found in mosaic 
form in almost all female members of a Polish family. Sanger sequencing of DNA 
from peripheral blood and from epithelial cells showed female mosaicism in three 
generations. This appears to be a new mechanism of inheritance and further 
research is required in order to understand the mechanism of this mosaicism. We 
conclude that BTHS genetic testing should include two or more tissues for women 
that appear to be noncarriers when blood DNA is initially tested. The results of 
our study should not only be applicable to BTHS families, but also to families 
with other X-linked diseases.