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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.

Symptoms

Symptoms include:

  • Delayed puberty
  • Down-slanting or wide-set eyes
  • Hearing loss (varies)
  • Low-set or abnormally shaped ears
  • Mild intellectual disability (only in about 25% of cases)
  • Sagging eyelids (ptosis)
  • Short stature
  • Small penis
  • 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.

Tests depend on the symptoms, but may include:

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

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. Hypofunction of the testes. In: Kliegman RM, Stanton BF, St. Geme JW, Schor NF, eds. Nelson Textbook of Pediatrics. 20th ed. Philadelphia, PA: Elsevier; 2016:chap 583.

Cooke DW, Divall SA, Radovick S. Normal and aberrant growth in children. In: Melmed S, Polonsky KS, Larsen PR, Kronenberg HM, eds. Williams Textbook of Endocrinology. 13th ed. Philadelphia, PA: Elsevier; 2016:chap 24.

Madan-Khetarpal S, Arnold G. Genetic disorders and dysmorphic conditions. In: Zitelli BJ, McIntire SC, Nowalk AJ, eds. Zitelli and Davis' Atlas of Pediatric Physical Diagnosis. 7th ed. Philadelphia, PA: Elsevier; 2018:chap 1.

    • Pectus excavatum

      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

        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: 1/10/2018

      Reviewed By: Anna C. Edens Hurst, MD, MS, Assistant 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.

      The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- A.D.A.M., a business unit of Ebix, Inc. Any duplication or distribution of the information contained herein is strictly prohibited.
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