Clinical and Genetic Characterization of Noonan Syndrome in a Romanian Cohort from Transylvania: Details on PTPN11 c.922A>G Variant and Phenotypic Spectrum.

Background: Noonan syndrome (NS) is a genetically heterogeneous condition within the RASopathies spectrum, with distinctive craniofacial features, congenital heart defects, short stature, and variably present developmental delay. Most cases result from variants in genes regulating the RAS/MAPK pathway, with PTPN11 variants being the most frequent; the c.922A>G substitution being among the most commonly reported. Methods: This pilot study analyzed clinical and partial genetic features of NS in a cohort from Transylvania, evaluated in the Children's Emergency Clinical Hospital in Cluj-Napoca. Thirty-one patients fulfilling the Van der Burgt diagnostic criteria (twenty-two males, nine females) were included. Clinical data were systematically reviewed, and targeted molecular testing for the PTPN11 c.922A>G variant was performed. Results: Congenital heart defects were highly prevalent, with pulmonary stenosis representing the most frequent anomaly (54.8%). Craniofacial dysmorphism was observed in 76.7% of cases, cryptorchidism in 50% of the males, and short stature below the third percentile was described in 77.4% of patients. Genetic screening identified the PTPN11 c.922A>G variant in two individuals (6.45%). Additional diagnoses included Williams-Beuren syndrome and a 17q11.2 deletion consistent with Neurofibromatosis-Noonan syndrome, underscoring the clinical and genetic heterogeneity of the cohort. Comparison with international reports highlighted variability in phenotype and variant frequency. Future research directions include Sanger sequencing of key PTPN11 exons and the application of next-generation sequencing targeting all RAS pathway genes. Conclusions: This is the first Romanian cohort study on patients with a clinical suspicion of NS, providing insight into their evaluation. The findings reinforce the need for comprehensive molecular approaches, facilitating diagnostic precision and counseling strategies.