Abstract

Noonan Syndrome (NS) is a RASopathy with a high burden of congenital heart disease. This study aims to summarize the demographic characteristics, cardiovascular findings, genetic results, applied interventions, and follow-up outcomes of pediatric NS cases followed at our center. Pediatric NS cases followed between December 2017 and August 2025 were examined in a single-center, retrospective, and descriptive design. Demographic data, echocardiography (ECHO) and 12-lead electrocardiography (ECG) findings, genetic analysis results, cardiac interventions, and follow-up outcomes were compiled from electronic records. Continuous variables were summarized descriptively. Nine children were included in the study (median age 8 years; range 2 months–14 years; 66.7% female). The most common accompanying pathology was pulmonary stenosis (PS, 6/9; 66.7%). Among the pulmonary stenosis cases, it was mild in one, moderate (valvular) in one, severe in three (two valvular, one associated with valve dysplasia/severe pulmonary artery hypoplasia), and borderline moderate-severe in one. Hypertrophic cardiomyopathy (HCM) was detected in 3/9 (33.3%) cases (1 obstructive, 2 non-obstructive). Other associated pathologies included atrial septal defect (ASD, 3/9), ventricular septal defect (VSD, 1/9), bicuspid aortic valve (BAV, 1/9), and mitral valv prolapsusu (MVP, 1/9). In genetic analysis, PTPN11 was dominant (5/9, 55.6%); RAF1 mutation was detected in two cases, SOS1 and KRAS mutations were each found in one case. Four patients (44.4%) underwent surgery: three underwent balloon pulmonary valvuloplasty and one with obstructive HCM underwent septal myectomy+mitral repair. In this pediatric NS series, PS was the dominant lesion, and HCM was a significant source of morbidity. Ballon valvuloplasty outcomes appear to be sensitive to valve morphology, and an early surgical approach may be appropriate for persistent/recurrent gradients. The findings emphasize the importance of structured follow-up supported by genotype information and point to the need for larger multicenter studies.

Key words: Noonan syndrome, RASopathy, pulmonary stenosis, hypertrophic cardiomyopathy, pediatric cardiology