Noonan syndrome is a genetic defect that causes a number of physical abnormalities, including short stature, heart defects, and an abnormal appearance.
A gene is a segment of deoxyribonucleic acid (DNA) and contains the code for a specific protein that functions in one or more types of cells in the body. Genes contain instructions that determine how the body is supposed to look and function. (See Genes and Chromosomes for a discussion about genetics.)
Noonan syndrome is caused by mutations in certain genes that can be inherited from a parent who has an affected gene. It also can occur spontaneously in a child whose parents do not have an affected gene. One of several different genes may be involved.
Noonan syndrome is relatively common, occurring in about 1 in 1,000 to 2,500 people. Both boys and girls can be affected.
Symptoms of Noonan Syndrome
Children may have webbing of the neck, low-set ears, droopy eyelids, widely spaced eyes, shortened fourth (ring) fingers, a high-arched palate, and heart abnormalities. Hearing problems can occur, and intelligence may be impaired. Most affected people are short.
Boys may have underdeveloped or undescended testes. Puberty may be delayed for both boys and girls, and young men with Noonan syndrome may have low levels of testosterone and be infertile. Girls usually begin menstruating somewhat later than unaffected girls, but fertility is typically normal.
Diagnosis of Noonan Syndrome
Genetic testing
To confirm the diagnosis of Noonan syndrome, genetic tests are done.
Treatment of Noonan Syndrome
Surgical repair of heart defects
Growth hormone therapy
For boys, sometimes testosterone hormone replacement therapy
There is no cure for Noonan syndrome. However, some specific symptoms and problems caused by the syndrome can be treated. Doctors monitor and repair heart defects as needed.
Children suspected of having Noonan syndrome should be evaluated for heart, vision, and hearing problems.
