Noonan Syndrome

Alternative Names

Noonan Syndrome

What is Noonan Syndrome

Noonan syndrome is a genetic disorder that prevents normal development in various parts of the body. A person can be affected by Noonan syndrome in various ways: unusual facial characteristics, short stature, heart defects, other physical problems and possibly lower intelligence.

It is caused by a genetic mutation and is acquired when a fetus inherits a copy of an affected gene from a parent (dominant inheritance). It can also occur as a spontaneous mutation, meaning there's no family history involved.

Signs and symptoms

Noonan syndrome occurs in approximately 1 in 1,000 to 2,500 people.

Signs and symptoms include:

• Delayed puberty
• Down-slanting or wide-set eyes
• Hearing loss (varies)
• Low-set or abnormally shaped ears
• Mild mental retardation (only in about 25% of cases)
• Sagging eyelids (ptosis)
• Short stature
• Small penis
• Undescended testicles
• Unusual chest shape (usually a sunken chest called pectus excavatum)
• Webbed and short-appearing neck

Possible complications

Complications and sequelae of Noonan Syndrome include:

• Webbed neck
• Micrognathia
• Lymphoedema
• Blepharoptosis
• Learning disability
• Pectus carinatum
• High arched palate
• Gynaecomastia
• Delayed puberty
• Pectus excavatum
• Atrial septal defect
• Facies abnormality
• Dysarthria
• Hypertrophic cardiomyopathy
• Pulmonary valve stenosis
• Cubitus valgus
• Hypogonadic hypogonadism
• Hypertelorism, ocular
• Cryptorchism (maldescended or ectopic testis)

What causes

To research the causes of Noonan Syndrome, consider researching the causes of these diseases that may be similar, or associated with Noonan Syndrome:

• Congenital genetic condition
• Down's syndrome
• Pulmonary stenosis
• Cardiomyopathy
• Failure to thrive
• Crytorchidism
• Clumsiness
• Poor co-ordination

Prevention

If you have a family history of Noonan syndrome, consult with your doctor about undergoing genetic counseling before you have children. However, because many of the cases of this disease occur spontaneously, there's no known way to prevent it.

If Noonan syndrome is detected early; it's possible that ongoing and comprehensive care may lessen some of its complications, such as heart disease.

Treatment

For today there is no known treatment for Noonan syndrome. Treatment focuses on the individual symptoms. Growth hormone has been used successfully to treat short stature in some persons with Noonan syndrome.