# Neurofibromatosis-Noonan syndrome: a prospective monocentric study of 26 patients and literature review

## TL;DR

This study identifies key clinical features of Neurofibromatosis-Noonan syndrome and highlights the importance of cardiovascular screening and facial recognition tools in diagnosis.

## Contribution

The study provides a detailed clinical characterization of NF-NS and validates the use of Face2Gene® for diagnostic agreement.

## Key findings

- NF-NS is marked by Noonan-like facial features and a high frequency of pectus excavatum.
- Face2Gene® showed high diagnostic concordance with clinicians for facial phenotype assessment.
- Congenital heart malformations, particularly pulmonic stenosis, are common in NF-NS patients.

## Abstract

Data on clinical manifestations of neurofibromatosis-Noonan syndrome (NF-NS) remain heterogeneous, with limited validated descriptions.

This study aims to better define the clinical and molecular features of NF-NS and compare them with existing literature. Secondary objectives include evaluating inter-rater diagnostic agreement among experienced clinicians and assessing the utility of deep-learning algorithms (Face2Gene® [F2G]). Additionally, we assess the prevalence of congenital heart malformations (CHM) in NF-NS compared to ‘classic’ neurofibromatosis type 1 (NF1). A 9-year, prospective, monocentric study was conducted, involving patients with NF1 pathogenic variants (PVs) and Noonan syndrome-like facial phenotype (NSLFP).

Twenty-six patients were enrolled. NSLFP was categorized as ‘suggestive’ in 69% of cases and ‘typical’ in 31%. The presence of at least two facial abnormalities (e.g., low-set ears, downslanted palpebral fissures, hypertelorism, and ptosis) was consistently observed in ‘typical’ cases. Inter-rater concordance was substantial (0.65 [95% CI = 0.56; 0.74]), while concordance between clinicians and F2G was almost perfect at (0.821 [CI 95% = 0.625; 1.000]). Missense NF1 PVs were observed in 38.5% of cases. Apart from NSLP and a high frequency of pectus excavatum (62.5%), no significant differences in anthropometric, dermatological, neurological, skeletal, or ocular clinical features were observed between NF-NS and ‘classic’ NF1. CHM were found in 19.2% of NF-NS patients, with pulmonic stenosis present in 7.7%.

NF-NS is a distinct phenotypic variant of NF1, marked by NSLP with consistent facial features -, and frequent pectus excavatum. F2G demonstrated high diagnostic concordance, reinforcing its clinical utility. Given the elevated risk of CHM, especially pulmonic stenosis, proactive cardiovascular assessment similar to other RASopathies is recommended for NS-NF patients, regardless of NF1 PV type.

The online version contains supplementary material available at 10.1186/s13023-025-03706-3.