Noonan Syndrome: A Comprehensive Review from Clinical Delineation to the Molecular Era of RASopathies and Lifelong Cardiologic Management

Noonan syndrome (NS) is a paradigmatic rare, genetically heterogeneous, multisystem disorder belonging to the RASopathies family, caused by dysregulated RAS/MAPK signaling. It is characterized by distinctive craniofacial features, postnatal short stature, and a high prevalence of congenital cardiac defects, with pulmonary valve stenosis (PS) and hypertrophic cardiomyopathy (HCM) being the hallmark lesions. First described by Dr. Jacqueline Noonan in 1968, the molecular era began with the discovery of PTPN11 mutations in 2001, revolutionizing diagnosis, risk stratification, and understanding of pathogenesis. Strong genotype–phenotype correlations now guide prognosis and personalized management; for instance, RAF1 and RIT1 variants confer a high risk of severe, early-onset HCM, while PTPN11 is strongly linked to dysplastic PS. Cardiac involvement remains the central determinant of long-term outcomes, requiring continuous surveillance from the prenatal period through adulthood. Management is inherently multidisciplinary, addressing endocrine, hematologic, neurodevelopmental, and oncologic aspects. Recent consensus statements emphasize the critical need for structured transition from pediatric to adult care. Novelty arises from the potential of MEK inhibitors as targeted therapies for severe HCM and lymphatic complications. This review provides a comprehensive update on NS, integrating foundational clinical knowledge with contemporary molecular insights, advanced cardiologic management, and emerging frontiers in therapy and diagnostics, underscoring the necessity of a proactive, lifelong, and personalized care approach.