Rare congenital X-linked disorder of lipid metabolism. Barth syndrome is transmitted in an X-linked recessive pattern. The syndrome is characterized by muscular weakness, growth retardation, DILATED CARDIOMYOPATHY, variable NEUTROPENIA, 3-methylglutaconic aciduria (type II) and decreases in mitochondrial CARDIOLIPIN level. Other biochemical and morphological mitochondrial abnormalities also exist.