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Noonan's Syndrome

Pat O'Connor

Revised: Dec. 20. 2011



A familial condition similar to both Turner Syndrome. It is different however, in that here is no chromosomal defect as is involved with Turner and unlike Noonan's, this condition can affect both sexes.

Though an early description of the syndrome is credited to a Russian medical student, Koblinsky, at the Russian/Estonian University at Dorpat, the condition is named after an American cardiologist, Jacquline A. Noonan. She and pediatrician Dorothy Ehmke conducted an extensive clinical study of 833 children with congenital heart disease. Their findings were published and reported to the Midwest Society of Pediatric Research held in Cincinnati in 1962.

Cardiac abnormalities occur in 50% of patients: these include pulmonary valve stenosis, thick and dysplastic pulmonary valves, right heart anomalies and left ventricular cardiomyopathy.

Symptoms of the disorder include not only heart indications but valvular pulmonary stenosis, short stature, hypertelorism and skeletal anomalies, and, in boys, retentio testis.

Skin manifestations present as transient lymphedema, in the dorsal hands during infancy and progresses to stasis in adulthood. Scalp findings include low posterior neck hairline and coarse curly hair. Scanty pubic, axillary, and beard hair growth has been noted. Nails show short and wide dystrophic changes.


Individuals who have Noonan syndrome have normal chromosome studies. Four genes - PTPN11, SOS1, RADF1 and KRAS- are the only genes that are known to be associated with Noonan syndrome. Approximately 50 percent of individuals with Noonan syndrome have mutations in the PTPN11 gene. Twenty percent of those with Noonan Syndrome have mutations in the SOS1. Mutations in the RAF1 gene account for between 10 and 15 percent of Noonan syndrome cases. About 5 percent of people with Noonan syndrome have mutations in the KRAS gene and usually have a more severe or atypical form of the disorder. The cause of Noonan syndrome in the remaining 10 to 15 percent of people with this disorder is not yet known.  (1)


Noonan Syndrome

Author: Jennifer Ibrahim, MD, Fellow, Department of Pediatrics, Division of Genetics, Children's Hospital of New Jersey and Mount Sinai School of Medicine

Coauthor(s): Margaret McGovern, MD, PhD, Vice Chair, Associate Professor, Department of Human Genetics, Mount Sinai School of Medicine


The Noonan Syndrome Support Group


Noonan Syndrome

National Organizations for Rare Disorders

Synonyms of Noonan Syndrome

Disorder Subdivisions

General Discussion
Noonan syndrome is a rare genetic disorder that is typically evident at birth (congenital). The disorder may be characterized by a wide spectrum of symptoms and physical features that vary greatly in range and severity. In many affected individuals, associated abnormalities include a distinctive facial appearance; a broad or webbed neck; a low hairline in the back of the head; and short stature. Characteristic abnormalities of the head and facial (craniofacial) area may include widely set eyes (ocular hypertelorism); vertical skin folds that may cover the eyes' inner corners (epicanthal folds); drooping of the upper eyelids (ptosis); a small jaw (micrognathia); a low nasal bridge; and low-set, prominent, abnormally rotated ears (pinnae). Distinctive skeletal malformations are also typically present, such as abnormalities of the breastbone (sternum), curvature of the spine (kyphosis and/or scoliosis), and outward deviation of the elbows (cubitus valgus). Many infants with Noonan syndrome also have heart (cardiac) defects, such as obstruction of proper blood flow from the lower right chamber of the heart to the lungs (pulmonary valvular stenosis). Additional abnormalities may include malformations of certain blood and lymph vessels, blood clotting and platelet deficiencies, mild mental retardation, failure of the testes to descend into the scrotum (cryptorchidism) by the first year of life in affected males, and/or other symptoms and findings.

In some affected individuals, Noonan syndrome appears to result from spontaneous (sporadic) genetic changes (mutations). In others, the disorder may be transmitted as an autosomal dominant trait. Genetic analysis of one affected multigenerational family (kindred) suggests that the disorder may result from mutations of a gene located on the long arm (q) of chromosome 12 (12q24). However, many investigators indicate that Noonan syndrome may be caused by mutations of different genes (genetic heterogeneity).

Organizations related to Noonan Syndrome


Noonan syndrome

Alternative names    

Turner-like syndrome of males


Noonan syndrome is a genetic disorder that causes abnormal development of multiple parts of the body. In particular there is webbing of the neck and different shapes to the chest that are reminiscent of Turner syndrome, hence the former name Turner-like syndrome. 

Causes, incidence, and risk factors    

Noonan syndrome can be inherited in an autosomal dominant manner. It affects at least 1 in 2,500 children. The fact that some children do not have a parent with Noonan syndrome likely reflects sporadic inheritance, that is, presumably the occurrence of a new mutation. The first specific gene that causes Noonan syndrome, called PTPN11, was discovered in 2001. It is expected that other genes will be discovered that cause Noonan syndrome.

Frequently seen abnormalities include webbing of the neck, changes in the sternum (usually a sunken chest called pectus excavatum), facial abnormalities, and congenital heart disease (especially pulmonic stenosis). Because these abnormalities resemble those of Turner syndrome (which only affects females), Noonan syndrome used to be called "male Turner syndrome," this term is no longer used because Noonan syndrome can affect females also.

Facial abnormalities may include low-set or abnormally shaped ears, sagging eyelids (ptosis), wide-set eyes (hypertelorism), epicanthal folds, and a small jaw (micrognathia). Mild mental retardation is present in about 25% of cases. Hearing loss varies. Puberty is usually delayed, and males may have undescended testicles and a small penis. Adult height is usually decreased.

Symptoms     Signs and tests    

Examination may show an extra fold of skin above the eyes (epicanthal folds). The eyes may also appear down-slanted (antimongoloid palpebral slant). The arms may be held at an unusual angle (cubitus valgus). There may be signs of congenital heart disease (often pulmonic stenosis, occasionally ASD). There may be a bleeding tendency revealed by low platelet count or coagulation tests and measuring the levels of specific coagulation factors in the blood (factors XI-XIII).

Testing will depend on the symptoms present. For example, if there are signs of heart disease, an ECG, chest X-ray or echocardiogram may be recommended. Hearing tests are indicated if there is any sign of decreased hearing.

Genetic testing has two purposes. First, a karyotype analysis can make sure that no easily detected abnormality of chromosomes can be mistaken for Noonan syndrome. Second, research genetic testing for mutations in the PTPN11 gene may be available.

Treatment     There is no single treatment for Noonan syndrome. Treatment focuses on the problems that occur. Growth hormone has been used successfully in Noonan syndrome to treat short stature.

Support Groups    

The Noonan Syndrome Support Group, Inc. 888-686-2224;

Expectations (prognosis)   

The expected outcome depends on the extent and severity of symptoms that are present. Patients can lead normal lives. Mental retardation, if present, is usually mild.


Calling your health care provider    This condition may be detected on early infant examinations. Evaluation by an experienced geneticist is often needed to determine a diagnosis of Noonan syndrome. If there are any signs of Noonan or Turner syndrome ask your health care provider for the name of a geneticist to see. Genetic counseling is recommended if you have a family history of Noonan syndrome. 


People with a family history of Noonan syndrome may want to consult with their health care provider before having children, although at this time there are no tests to detect the tendency for this disorder. Prevention of complications, such as heart disease, depends on early detection and continuing care of a cardiologist.

Update Date: 8/6/2003


-------------Abstracts and Studies------ 

Bleeding disorders in Noonan syndrome

Feb 2012


Noonan S yndrome: Clinical Features, Diagnosis, and Management Guidelines 

Key Words:  Noonan syndrome; PTPN11; SOS1; BRAF; KRAS; NRAS; RAF1; SHOC2;  signal transduction; congenital heart disease, short stature

Noonan syndrome (NS) is a relatively common congenital genetic disorder with an estimated prevalence of 1 in 1000 to 1 in 2500 live births.1 Characteristic findings include distinctive facial features, short stature, chest deformity, and congenital heart disease. It is an autosomal dominant disorder with complete penetrance but variable expressivity. Until recently, diagnosis was based solely on clinical findings, but genetic mutations are identifiable in ∼61% of the patients. Because of the difficulty in establishing a diagnosis of NS, the Noonan Syndrome Support Group coordinated a meeting of health care providers with expertise in various aspects of the disorder with the aim of developing guidelines for its diagnosis and management. This report is the result of those efforts and is intended to provide the pediatrician with key clinical features of NS, to provide an update of currently understood genetic causes, and to present management recommendations 

See remainder of article:


Noonan syndrome

What is Noonan Syndrome?

Noonan syndrome is a disorder that involves unusual facial characteristics, short stature, heart defects present at birth, bleeding problems, developmental delays, and malformations of the bones of the rib cage.

Noonan syndrome is caused by changes in one of several autosomal dominant genes. A person who has Noonan syndrome may have inherited an altered (mutated) gene from one of his or her parents, or the gene change may be a new change due to an error carried by the egg or sperm or occurring at conception. Alterations in four genes - PTPN11, SOS1, RAF1 and KRAS - have been identified to date.

Noonan syndrome is present in about 1 in 1,000 to 1 in 2,500 people.

See remainder of article: Reference #(1.)  National Human Genome Research Institute


The benefits of growth hormone therapy in patients with Turner syndrome,Noonan syndrome and children born small for gestational age. 

Dec 2011


Rosette forming glioneuronal tumor in association with Noonan syndrome: pathobiological implications. 

Nov-Dec 2011


Two cases of Noonan syndrome: aortic coarctation causing a giant aneurysm of the descending aorta. 

Oct 2011


Anesthetic considerations and difficult airway management in a case of Noonan syndrome

Jul 2011


Bleeding from the small intestine and aortic regurgitation in Noonan syndrome



Short stature and its treatment in Turner and Noonan syndromes.

Feb. 2010


Noonan's syndrome


Noonan's Syndrome


Noonan's Syndrome


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