Barth syndrome is an X-bound inherited recessive disorder with the prevalenсe 1:300000 — 1:400000 of live bornt, caused by mutations in the gene TAZ; manifesting with dilation cardiomyopathy, neutropenia, proxymal myopathy, delayed physical and motoric development. In the article, a clinical case provided of the Barth syndrome, confirmed by target sequencing of TAZ gene in a boy of 1st year of life, presented in 3 months age by an episode of infectious disease and dilation cardiomyopathy, with family anamnesis of sudden death at the moment of infectious disease in the grand uncle of proband. In dynamics, the patient showed delayed motoric development, as the delay in mass and height (<3 percentile), persistent absolute neutropenia, stable high levels of cardiospecific enzymes, NT-proBNP, symptomes of severe heart failure with following fatal outcome at age of 12 months from sudden death during an episode of infectious disease. The multidisciplinarity presented, as the necessity for clear understanding by practitioners of the specific
