Infective endocarditis (IE) in the course of hypertrophic cardiomyopathy (HCM) is a rare complication, however, it is a serious therapeutic problem (1-4). According to some authors, the probability of IE in patients with HCM within 10 years is about 5% (2). The risk of endocarditis is particularly high in patients with obstruction of the left ventricular outflow tract (LVOTO) and the high value of the systolic pressure gradient in the left ventricular outflow tract (1-6). In the echocardiography bacterial vegetations are usually located on the anterior mitral valve leaflet, on the aortic valve, or both. The inflammatory process can damage the heart valves, cause of their significant regurgitation, what requires urgent cardiac surgery (1-3, 5-7).

Currently, 17 year old boy, in whom hypertrophic obstructive cardiomyopathy was diagnosed at the age of 5 years. Since the age of 10 year, he was taken care of a pediatric cardiologist in the district center. From November 2010 (at the age of 15) the patient reported feeling worse, increasing fatigability. In December 2010, he was hospitalized in pediatric cardiology referral center, where the elevated values of inflammatory markers, thickening of the mitral valve leaflets and third degree mitral regurgitation were found. In the chest X-ray pneumonia was diagnosed, and intravenous antibiotic therapy (cefuroxime) has been applied. In January 2011 the boy was urgently admitted to the paediatric cardiology departament with fever 38 degrees, with marked dyspnoea at rest. Tachycardia 137/min, systolic murmur 3/6 scale of Levin along the left sternal border and at the apex of the heart and liver enlargement were present. In the chest X-ray bilateral parenchymal density, features of chronic congestion in the pulmonary circulation, enlarged cardiac silhouette (cardio-thoracic ratio 0.56) were found. The values of the inflammatory markers were increased, while the blood cultures obtained were negative. The antibiotics (clarithromycin and cefuroxime) have been taken for 11 days to give a slight reduction of the inflammatory markers and the alleviation of fever. In echocardiography features of hypertrophic obstructive cardiomyopathy were present: the thickness of the interventricular septum was 17.9 mm (normal values indexed to the body surface area 4.9-8.5 mm), the thickness of the left ventricle posterior wall was 11 mm (normal values corrected to the body surface area 4.3-9.5 mm), obstruction of the left ventricular outflow tract with the maximum systolic pressure gradient 100 mmHg, systolic motion of the anterior mitral leaflet and its adherence to the hypertrophied interventricular septum and the mitral valve regurgitation third degree also were found (fig. 1, 2).

Moreover, the presence of three bacterial vegetation on the anterior mitral valve leaflet were visualised (one with a diameter of 4.5 mm moving into the left atrium, the second with a diameter of 6.2 mm at the end of the leaflet, the third of the diameter of 8mm in the middle of the leaflet) (fig. 3).