Noonan syndrome
Noonan syndrome is a disease present from birth (congenital) that causes many parts of the body to develop abnormally. In some cases it is passed down through families (inherited).
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 many ways that a trait or disorder can be passed down through families. In an autosomal dominant disease, if you get the...
Read Article Now Book Mark ArticleSymptoms
Symptoms include:
- Delayed puberty
- Down-slanting or wide-set eyes
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Hearing loss (varies)
Hearing loss
Hearing loss is being partly or totally unable to hear sound in one or both ears.
Read 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 eyelid. The edge of the upper eyelid may be lower than it should be (ptosis) or there may be excess b...
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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
Pulmonic stenosis is a heart valve disorder that involves the pulmonary valve. This is the valve separating the right ventricle (one of the chambers ...
Read Article Now Book Mark ArticleAtrial 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...
Read Article Now Book Mark ArticleTests depend on the symptoms, but may include:
- Platelet count
- Blood clotting factor test
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ECG, chest x-ray, or echocardiogram
ECG
An electrocardiogram (ECG) is a test that records the electrical activity of the heart.
Read 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.
Read Article Now Book Mark Article - Hearing tests
- Growth hormone levels
- Renal ultrasound
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 people with Noonan syndrome.
Support Groups
More information and support for people with Noonan syndrome and their families can be found at -- www.teamnoonan.org.
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
Cooke DW, Divall SA, Radovick S. Normal and aberrant growth in children. In: Melmed S, Auchus RJ, Goldfine AB, Koenig RJ, Rosen CJ, eds. Williams Textbook of Endocrinology. 14th ed. Philadelphia, PA: Elsevier; 2020:chap 25.
Madan-Khetarpal S, Arnold G, Ortiz D. Genetic disorders and dysmorphic conditions. In: Zitelli BJ, McIntire SC, Nowalk AJ, Garrison J, eds. Zitelli and Davis' Atlas of Pediatric Physical Diagnosis. 8th ed. Philadelphia, PA: Elsevier; 2023:chap 1.
Mitchell AL. Congenital anomalies. In: Martin RJ, Fanaroff AA, Walsh MC, eds. Fanaroff and Martin's Neonatal-Perinatal Medicine. 11th ed. Philadelphia, PA: Elsevier; 2020:chap 30.
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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
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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: 1/6/2022
Reviewed By: Anna C. Edens Hurst, MD, MS, Associate Professor in Medical Genetics, The University of Alabama at Birmingham, Birmingham, AL. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.