Noonan Syndrome

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.

Causes

A gene mutation (change) causes Noonan syndrome. Many different gene mutations can cause it. Everyone has two copies of almost every gene. It only takes one changed gene to cause Noonan syndrome. In that case, children of a parent who has Noonan syndrome have a 50% chance of having it too. Very rarely, changes in both copies of one gene can cause Noonan syndrome.

Symptoms

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:

• Eyes are wide-set and down-slanting with droopy lids.
• Ears are low-set and rotated backward.
• Nose is depressed at the top, with a wide base and bulbous tip.
• Mouth has a deep groove between the nose and the mouth and wide peaks in the upper lip. The crease that runs from the edge of the nose to the corner of the mouth becomes deeply grooved with age. Teeth may be crooked, the inside roof of the mouth (palate) may be highly arched and the lower jaw may be small.
• Facial features may appear coarse, but appear sharper with age. The face may appear droopy and expressionless.
• Head may appear large with a prominent forehead and a low hairline on the back of the head.
• Skin may appear thin and transparent with age.

Heart Disease

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:

• Valve disorders. Pulmonary valve stenosis is a narrowing of the pulmonary valve, the flap of tissue that separates the lower right chamber (ventricle) of the heart from the artery that supplies blood to the lungs (pulmonary artery). It's the most common heart problem seen with Noonan syndrome, and it may occur alone or with other heart defects.
• Thickening of the heart muscle (hypertrophic cardiomyopathy). This is abnormal growth or thickening of the heart muscle that affects some people with Noonan syndrome.
• Other structural defects of the heart. The defects can involve a hole in the wall that separates the two lower chambers of the heart (ventricular septal defect), narrowing of the artery that carries blood to the lungs for oxygen (pulmonary artery stenosis), or narrowing of the major blood vessel (aorta) that carries blood from the heart to the body (aortic coarctation).
• Irregular heart rhythm. This can occur with or without structural heart abnormalities. Irregular heart rhythm occurs in the majority of people with Noonan syndrome.

Other Symptoms as the child grows might include:

• Starting to walk, talk, and other things later than most children
• Vision and hearing problems
• Learning and language problems
• Slow growth
• Short height
• Easy bruising and bleeding a lot (from periods, nosebleeds, cuts, etc.)
• Late puberty

The symptoms of Noonan syndrome can be mild to severe. Two children with Noonan syndrome may have completely different symptoms and skills.

Treatment

There's no cure for Noonan syndrome, but medical care can help with almost every symptom. e.g.

• Medicines and surgery can help heart problems.
• Medicines or blood transfusions can treat bleeding.
• Growth hormone or other medicine can help speed up slowed growth.
• Surgery can correct undescended testicles.
• Education programs can help a child who has trouble learning.
• Many children will have trouble with speech and language. Working with a speech therapist before problems start can make these problems milder.

The symptoms of Noonan syndrome can be mild to severe. Two children with Noonan syndrome may have completely different symptoms and skills.