RESUMO
Barth syndrome (BTHS) is an X-linked recessive disease caused by mutations in tafazzin gene (TAZ) which lead to cardiolipin deficiency and mitochondrial dysfunction. Male patients have variable clinical findings, including cardiomyopathy, skeletal myopathy, prepubertal short stature, neutropenia and 3-methylglutaconic aciduria. Female carriers are usually asymptomatic. We report a novel TAZ gene mutation in male and female siblings with left ventricular noncompaction and hypotonia. Additionally, the brother presented an intermittent neutropenia and increased urinary levels of 3-methylglutaconic and 3-methylglutaric acid. The molecular genetic testing showed that both siblings carry the mutation: c.253insC, p.(Arg85Profs*54) in exon 3 of the TAZ gene. This article presents the first case of BTHS in a heterozygous female patient with normal karyotype.