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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.
Author: Jennifer Ibrahim, MD, Fellow, Department of Pediatrics, Division of Genetics, Children's Hospital of New Jersey and Mount Sinai School of MedicineCoauthor(s): Margaret McGovern, MD, PhD, Vice Chair, Associate Professor, Department of Human Genetics, Mount Sinai School of Medicine
National Organizations for Rare Disorders
Synonyms of Noonan Syndrome:
Female Pseudo-Turner Syndrome
Male Turner Syndrome
Turner Phenotype with Normal Chromosomes (Karyotype)
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
Big Hearts for Little Hearts
365 Willis AvenueMineola NY 11501
Phone #: 516-741-5522800 #: --
NIH/National Heart, Lung and Blood Institute Information Center
P.O. Box 30105, Bethesda MD 20824-0105
Phone #: 301-592-8573800 #: --
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.
webbed and short appearing neck
sternum abnormalities (pectus excavatum, occasionally pectus carinatum)
sagging eyelids (ptosis)
wide-set (hypertelorism) or down-slanting eyes
low-set or abnormally shaped ears
mental retardation in only a quarter of patients
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.
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.
Mental retardation, if present, is usually mild.
social difficulties related to physical abnormalities
male infertility in those with both testes undescended
abnormal heart structure
accumulation of fluid in tissues of body (lymphedema, cystic hygroma)
failure to thrive in infants
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