Weerakkody Y, Elfeky M, Gaillard F, et al. Noonan syndrome. Reference article, Radiopaedia.org (Accessed on 19 Apr 2024) https://doi.org/10.53347/rID-11103
Noonan syndrome (NS) is a genetically and phenotypically heterogeneous non-aneuploidic congenital RASopathy. Affected individuals can bear some clinical features similar to that of Turner syndrome.
The inheritance is autosomal dominant although a significant proportion of cases are sporadic 8. Many genes have been implicated, the most common being the PTPN11 gene which encodes for SHP2, which results in an inability to inactivate SHP2 causing increased signaling of the Ras/MAPK pathway. However, other genes that may be less commonly implicated include SOS1, KRAS, RAF1, NRAS, and SHOC210. Because of its effect in amplifying the Ras/MAPK pathway, it is considered to be a RASopathy10.
Radiographic features
Antenatal ultrasound
Early 1st trimester ultrasound may show nuchal edema or a cystic hygroma similar to that of Turner syndrome. With subsequent scanning, some of the above individual clinical features may be present sonographically.
History and etymology
It is named after Jacqueline A Noonan (1928-fl 2019), an American pediatric cardiologist 11.
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6. George CD, Patton MA, El sawi M et-al. Abdominal ultrasound in Noonan syndrome: a study of 44 patients. Pediatr Radiol. 1993;23 (4): 316-8. - Pubmed citation
7. Rush WJ, Donnelly LF, Brody AS et-al. "Missing" sternal ossification center: potential mimicker of disease in young children. Radiology. 2002;224 (1): 120-3. doi:10.1148/radiol.2241011202 - Pubmed citation
9. Allanson JE, Roberts AE. Noonan Syndrome. 2001 Nov 15 [Updated 2016 Feb 25]. In: Pagon RA, Adam MP, Ardinger HH, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2016. Available from: http://www.ncbi.nlm.nih.gov/books/NBK1124/
11. Noonan JA, Kappelgaard AM. The efficacy and safety of growth hormone therapy in children with noonan syndrome: a review of the evidence. (2015) Hormone research in paediatrics. 83 (3): 157-66. doi:10.1159/000369012 - Pubmed