Diagnostic features of Noonan syndrome (NS) and the relative importance of these features3
| Feature | A=major | B=minor | ||
| 1.Facial | Typical face* | Suggestive face | ||
| 2.Cardiac | Pulmonary valve stenosis and/or hypertrophic cardiomyopathy | Other cardiac defect | ||
| 3.Height | <3rd centile | <10th centile | ||
| 4.Chest wall | Pectus carinatum/excavatum | Broad thorax | ||
| 5.Family history | First-degree relative with definite NS | First-degree relative suggestive of NS | ||
| 6.Other | Mild developmental delay, cryptorchidism AND lymphatic dysplasia | Mild developmental delay, cryptorchidism OR lymphatic dysplasia | ||
| Definitive NS= | Criterion 1A (typical face) PLUS | Criterion 1B (suggestive face) PLUS | ||
| 1×major criterion (2A‒6A) | 2×minor criteria (2B‒6B) | 2×major criteria (2A‒6A) | 3×minor criteria (2B‒6B) | |
*Facial features of NS vary over time and may have only subtle differences.