An 11-year-old patient arrived at the Republican Scientific and Practical Center of Pediatric Surgery with a rare pathology: thickening of the heart muscle, which disrupted the heart and could lead to organ transplantation. The child was in serious condition, with a marked violation of the blood flow of the organ. Potentially, the operation could be carried out in America, Germany, Turkey or in Belarus. Our specialists were the first to respond. The operation lasted 5 hours, of which the heart was stopped for 2 hours. Doctors removed the muscles that were disrupting the organ. Due to this, no transplantation was needed. Now the child's life is not in danger and by the end of the week the little patient will be able to return home.