Autosomal Dominant condition 

Ras-MAPK pathway Defect 

Due to mutation in 

    PTPN11 protein-tyrosine phosphatase,non-receptor-type 11) gene on chromosome 12. 

    10–15% are caused by SOS1 (son of seven-less homologue 1 (Drosophila), on

    chromosome and RAF1

NS is often associated with advanced paternal age 

Karyotype is usually normal.

Male: Female - 4:1

Phenotypically looks like Turner

So if male and looks like Turner think of Noonan. 

Clinical Features 


    Pulmonary valve stenosis (Most common)

    Hypertrophic cardiomyopathy 

    Branch pulmonary artery stenosis

    Septal defects 


    Webbed or short neck

    Pectus excavatum or carinatum

    Wide-spaced nipples

    Wide carrying angle (cubitus valgus)

    Short stature in 80%

Triangular facies

Antimongoloid slant


Low set ears and posteriorly rotated

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