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Noonan syndrome
Noonan syndrome is a disease that can be passed down through families (inherited). It causes many parts of the body to develop abnormally.
Causes
Noonan syndrome is linked to defects in several genes. In general, certain proteins involved in growth and development become overactive as a result of these gene changes.
Noonan syndrome is an autosomal dominant condition. This means only one parent has to pass down the nonworking gene for the child to have the syndrome. However, some cases may not be inherited.
Autosomal dominant
Autosomal dominant is one of several ways that a trait or disorder can be passed down (inherited) through families. In an autosomal dominant disease,...
Symptoms
Symptoms include:
- Delayed puberty
- Down-slanting or wide-set eyes
-
Hearing loss
(varies)
Hearing loss
Hearing loss is being partly or totally unable to hear sound in one or both ears.
ImageRead Article Now Book Mark Article - Low-set or abnormally shaped ears
- Mild intellectual disability (only in about 25% of cases)
-
Sagging eyelids (
ptosis
)
Ptosis
Eyelid drooping is excess sagging of the upper eylid. The edge of the upper eyelid may be lower than it should be (ptosis) or there may be excess ba...
ImageRead Article Now Book Mark Article -
Short stature
Short stature
A child who has short stature is much shorter than children who are the same age and sex. Your health care provider will go over your child's growth ...
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- Undescended testicles
- Unusual chest shape (most often a sunken chest called pectus excavatum)
- Webbed and short-appearing neck
Exams and Tests
The health care provider will perform a physical exam. This may show signs of heart problems the infant had from birth. These may include pulmonary stenosis and atrial septal defect .
Pulmonary stenosis
Pulmonary valve stenosis is a heart valve disorder that involves the pulmonary valve. This is the valve separating the right ventricle (one of the ch...
Atrial septal defect
Atrial septal defect (ASD) is a heart defect that is present at birth (congenital). As a baby develops in the womb, a wall (septum) forms that divide...
Tests depend on the symptoms, but may include:
- Platelet count
- Blood clotting factor test
-
EKG
,
chest x-ray
, or echocardiogram
EKG
An electrocardiogram (ECG) is a test that records the electrical activity of the heart.
ImageRead Article Now Book Mark ArticleChest x-ray
A chest x-ray is an x-ray of the chest, lungs, heart, large arteries, ribs, and diaphragm.
ImageRead Article Now Book Mark Article - Hearing tests
- Growth hormone levels
Genetic testing can help diagnose this syndrome.
Treatment
There is no specific treatment. Your provider will suggest treatment to relieve or manage symptoms. Growth hormone has been used successfully to treat short height in some persons with Noonan syndrome.
Support Groups
The Noonan Syndrome Foundation is a place where people dealing with this condition can find information and resources.
Possible Complications
Complications may include:
- Abnormal bleeding or bruising
- Buildup of fluid in tissues of body (lymphedema, cystic hygroma)
- Failure to thrive in infants
- Leukemia and other cancers
- Low self-esteem
- Infertility in males if both testes are undescended
- Problems with the structure of the heart
- Short height
- Social problems due to physical symptoms
When to Contact a Medical Professional
This condition may be found during early infant exams. A geneticist is often needed to diagnose Noonan syndrome.
Prevention
Couples with a family history of Noonan syndrome may want to consider genetic counseling before having children.
References
Ali O, Donohoue PA. Noonan syndrome. In: Kliegman RM, Stanton BF, St Geme JW, Schor NF, eds. Nelson Textbook of Pediatrics . 20th ed. Philadelphia, PA: Elsevier; 2016:chap 583.
Allanson JE, Roberts AE. Noonan syndrome. GeneReviews. Seattle, WA: University of Washington; 2011:11. www.ncbi.nlm.nih.gov/books/NBK1124/
-
Pectus excavatum - illustration
Pectus excavatum is a condition in which the "breast bone" (sternum) appears sunken and the chest concave. It is sometimes called "funnel chest". The majority of these cases are not associated with any other condition (isolated findings). However, some genetic conditions include pectus excavatum.
Pectus excavatum
illustration
-
Pectus excavatum - illustration
Pectus excavatum is a condition in which the "breast bone" (sternum) appears sunken and the chest concave. It is sometimes called "funnel chest". The majority of these cases are not associated with any other condition (isolated findings). However, some genetic conditions include pectus excavatum.
Pectus excavatum
illustration
Review Date: 1/25/2016
Reviewed By: Chad Haldeman-Englert, MD, FACMG, Fullerton Genetics Center, Asheville, NC. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.
