Diagnosis and Testing
What is the testing for Noonan syndrome?
If a diagnosis of Noonan syndrome is suspected in an infant or child, a genetics team can perform genetic testing to confirm a diagnosis. Genetic testing for Noonan sydndrome may be performed by a multi-gene panel, serial single-gene testing, and more comprehensive genomic testing.
A multi-gene panel that includes multiple genes associated with Noonan syndrome is the test of choice for an individual suspected of having Noonan syndrome. The features of Noonan syndrome have significant overlap with cardiofaciocutaneous syndrome (CFC) and Costello syndrome, most available panels include the genes for these diagnoses, too.
Serial single-gene testing can be considered if panel testing is not feasible. Approximately 50% of individuals with Noonan syndrome will have a pathogenic mutation (change) in the PTPN11 gene. Single-gene testing starting with PTPN11 would be the next best first test. Appropriate serial single-gene testing if PTPN11 testing is non-diagnostic can be determined by the individual's features.
More comprehensive genomic testing (if available) including whole-exome sequencing (WES) or whole-genome sequencing (WGS) may be considered if use of a multi-gene panel and/or serial single-gene testing fails to confirm a diagnosis in an individual with features of Noonan syndrome.