Noonan's syndrome

Noonan's syndrome is an inherited disorder resulting in abnormal development of many parts of the body. The cause is a defect in a gene that produces a specific protein, which is important in tissue development and cell function. This disorder occurs in at least one of every 2,500 births.

Noonan's syndrome can be inherited in an autosomal dominant manner. This means a child has to inherit only one copy of the affected gene from a parent to develop the disease. It can also occur as a spontaneous mutation — meaning it occurs with no family history of the disease.

Signs and symptoms of Noonan's syndrome may include:

• Unusual facial characteristics, such as low-set or abnormally shaped ears, sagging eyelids (ptosis) and a small jaw
• Short stature
• Broad, sunken chest (pectus excavatum)
• Short, webbed neck
• Undescended testicles in males
• Delayed puberty
• Deficient sex hormones (hypogonadism)
• Heart defects, primarily narrowing (stenosis) of the pulmonary valve or atrial septal defect
• Mental retardation

A doctor may make a diagnosis of Noonan's syndrome based on:

• Signs and symptoms
• Blood tests that detect the presence of the gene defect responsible for Noonan's syndrome

There's no cure for Noonan's syndrome. Treatment is directed at managing the signs and symptoms.