====== Noonan Syndrome ======
====Main Features====
  * Highly variable but most have short stature, mild intellectual disability or developmental delay and
  * Characteristic faces
    * High forehead
    * depressed nasal bridge
    * low-set posteriorly rotated ears with fleshy helices
{{::noonan_syndrome.png?direct&600|}}
{{::noonan_syndrome_child.png?direct&600|}}
Photos from [[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1049850/pdf/jmedgene00075-0018.pdf|J Med Genet. 1987;24(1):9-13.]]

====Eye Findings====
  * Refractive Errors:  Myopia, hyperopia and astigmatism
  * Ptosis
  * Hypertelorism
  * Downslanting palpebral fissures
  * Epicanthal folds
  * Keratoconus
  * vivid blue or blue-green iris
  * Posterior embryotoxin
  * Cataract
  * Strabismus
  * Nystagmus
  * Optic nerve hypoplasia
  * Optic nerve coloboma
====Other Findings====
  * Webbed or broad neck
  * Chiari Malformation 
  * Hydrocephalus
  * Macrocephaly
  * Craniosynostosis
  * Sensorineural deafness
  * Conductive hearing loss
  * Giant cell tumors of the jaw
  * Sternal deformities
    * pectus carinatum of the superior sternum
    * pectus excavated of the inferior sternum
  * Cardiovascular defects
    * Pulmonic stenosis
    * hypertrophic cardiomyopathy 
    * ASD
    * VSD
    * lymphatic dysplasia 
  * Chyptorchidism 
  * Infertility 
  * Hematologic abnormalities
    * elevation in PT/PTT
    * abnormal platelets, count and function 
====Etiology====
  * Genetic disorder of the genes in the RAS-MAPK pathway
    * PTPN11 (50%)
    * SOS1 (13%)
    * RAF1 (5%)
    * RIT1 (5%)
    * others
      * KRAS, BRAF, LZTR1, NRAS
  * This pathway is important in cellular differentiation and proliferation 
  * Autosomal dominant inheritance most commonly with 2/3 denovo 
  * Associated with advanced paternal age 
====Reference====
  * [[https://doi.org/10.1007/s00431-018-3183-1| van Trier, et al. Ocular findings in NS: a retrospective cohort study of 105 patients. European Journal of Pediatrics. 2018;177(8):1293–1298]]
  * [[https://www.aaojournal.org/article/S0161-6420(16)30594-2/fulltext|van Trier et al. Ocular Manifestations of Noonan Syndrome: A Prospective Clinical and Genetic Study of 25 Patients. Ophthalmology.2016;123(10):2134-2146]]
  * [[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1049850/pdf/jmedgene00075-0018.pdf|Allanson, JE. Noonan Syndrome. J Med Genet. 1987;24(1):9-13.]]
  * [[https://eyewiki.aao.org/Noonan_Syndrome#Ophthalmic_presentation|eyeWiki]]

{{tag>syndrome}}