Noonan syndrome other diagnostic studies
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Serge Korjian
Overview
Although not always required, genetic testing can confirm the diagnosis but not exclude it. Classically PTPN11 mutations can be seen in 60% of patients.
Other Diagnostic Studies
Genetic Analysis
Eight genes all involved in the RAS/MAP kinase pathway have been identified as possible causes for Noonan syndrome. In order of prevalence, the causative mutations involve the following genes: PTPN11, SOS1, RAF1, SHOC2, KRAS, BRAF, NRAS, and CBL. Definitive diagnosis is usually with genetic testing which is commonly by chip-based sequencing, to test all the genes that could be involved simultaneously. [1] If chip based-testing is not available, PTPN11 sequencing should be performed first. If PTPN11 is negative considering other genes can be based on the clinical findings detailed below:[2]
- SOS1: Absent developmental delays, normal stature, skin and hair findings
- RAF1: Hypertrophic cardiomyopathy
- KRAS: Significant developmental delay and cognitive impairment
- SHOC2: Thin, slow-growing, sparse hair
Not all patients require genetic testing as the diagnosis is mostly clinical. A positive genetic test can confirm the diagnosis, but a negative test cannot exclude it.[2]
References
- ↑ Roberts AE, Allanson JE, Tartaglia M, Gelb BD (2013). "Noonan syndrome". Lancet. 381 (9863): 333–42. doi:10.1016/S0140-6736(12)61023-X. PMID 23312968.
- ↑ 2.0 2.1 Romano AA, Allanson JE, Dahlgren J, Gelb BD, Hall B, Pierpont ME; et al. (2010). "Noonan syndrome: clinical features, diagnosis, and management guidelines". Pediatrics. 126 (4): 746–59. doi:10.1542/peds.2009-3207. PMID 20876176.
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