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, Yazan Daaboul


Although not always required, genetic testing can confirm the diagnosis but not exclude it. Classically PTPN11 mutations can be seen in approximately half of the 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]


  1. 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. 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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