Pulmonary stenosis as a predisposing factor for infective endocarditis in a patient with Noonan syndrome

Noonan syndrome is an autosomal dominant dysmorphic syndrome. Pulmonary stenosis is the most common cardiac anomaly in Noonan patients, with an incidence of 60%. A 9-year-old girl was referred to our institution with pericardial effusion. Transthoracic echocardiography indeed confirmed massive pericardial effusion and revealed, further, valvular and arterial pulmonary vegetations that accompanied a dysplastic tricuspid pulmonary valve. We decided to perform emergency pericardial tube drainage and to continue the anti-biotic regimen for 2 more weeks before undertaking open-heart surgery. After 2 weeks, the patient underwent an operation wherein the valvular vegetations were excised and a pulmonary valve commissurotomy was performed, yielding a competent pulmonary valve with 3 distinct but moderately dysplastic cusps. In addition to the pulmonary valve, the main, left, and right pulmonary arteries were filled with mobile vegetations, which were removed during the procedure. In this patient, a dysplastic and stenotic pulmonary valve may have contributed to the progression of endocarditis and to the growth of vegetations that occupied the pulmonary arteries. In conclusion, we hypothesize that although pulmonary stenosis is not considered a common predisposing factor for infective endocarditis, it can contribute to the progression of infective endocarditis in Noonan patients.