Noonan syndrome

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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 a wide variety of ways. These include unusual facial characteristics, short stature, heart defects, other physical problems and possible developmental delays.

Noonan syndrome is caused by a genetic mutation and is acquired when a child 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.

Management of Noonan syndrome focuses on controlling the disorder’s symptoms and complications. Growth hormone may be used to treat short stature in some people with Noonan syndrome.

Signs and symptoms of Noonan syndrome vary greatly among individuals and may be mild to severe. Characteristics may be related to the specific gene containing the mutation.

Facial appearance is one of the key clinical features that leads to a diagnosis of Noonan syndrome. These features may be more pronounced in infants and young children, but change with age. In adulthood, these distinct features become more subtle.

Features may include the following:

Many people with Noonan syndrome are born with some form of heart defect (congenital heart disease), accounting for some of the key signs and symptoms of the disorder. Some heart problems can occur later in life. Some forms of congenital heart disease associated with this disorder include:

Noonan syndrome can affect normal growth. Many children with Noonan syndrome don’t grow at a normal rate. Issues may include the following:

Some common issues can include:

Intelligence isn’t affected for most people with Noonan syndrome. However, individuals may have:

A common sign of Noonan syndrome is abnormalities of the eyes and eyelids. These may include:

Noonan syndrome can cause hearing deficits due to nerve issues or to structural abnormalities in the inner ear bones.

Noonan syndrome can cause excessive bleeding and bruising due to clotting defects or having too few platelets.

Noonan syndrome can cause problems with the lymphatic system, which drains excess fluid from the body and helps fight infection. These problems:

Many people, especially males, with Noonan syndrome can have problems with the genitals and kidneys.

People with Noonan syndrome may have skin conditions, which most commonly are:

The signs and symptoms of Noonan syndrome can be subtle. If you suspect you or your child may have the disorder, see your primary care doctor or your child’s pediatrician. You or your child may be referred to a geneticist or a cardiologist.

If your unborn child is at risk because of a family history of Noonan syndrome, prenatal tests may be available.

In an autosomal dominant disorder, the mutated gene is a dominant gene located on one of the nonsex chromosomes (autosomes). You need only one mutated gene to be affected by this type of disorder. A person with an autosomal dominant disorder — in this case, the father — has a 50 percent chance of having an affected child with one mutated gene (dominant gene) and a 50 percent chance of having an unaffected child with two normal genes (recessive genes).

Noonan syndrome is caused by a genetic mutation. These mutations can occur in multiple genes. Defects in these genes cause the production of proteins that are continually active. Because these genes play a role in the formation of many tissues throughout the body, this constant activation of proteins disrupts the normal process of cell growth and division.

The mutations that cause Noonan syndrome can be:

A parent with Noonan syndrome has a 50 percent chance (one chance in two) of passing the defective gene on to his or her child. The child who inherits the defective gene may have fewer or more symptoms than the affected parent.

Complications can arise that may require special attention, including:

Because some cases of Noonan syndrome occur spontaneously, there’s no known way to prevent it. However, if you have a family history of this syndrome, talk to your doctor about the benefits of genetic counseling before you have children. Noonan syndrome can be detected with molecular genetic testing.

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

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Noonan syndrome

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