Children's Hospital Colorado

Noonan Syndrome in Children

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What is Noonan syndrome?

Noonan syndrome is a genetic disorder that affects the whole body, including the heart, blood vessels, skeletal system, eyes, ears and brain. Noonan syndrome is part of a group of conditions called the “RASopathies.” They are called RASopathies because they are caused by problems in the RAS/mitogen-activated protein kinase (MAPK) pathway, a cell communication system that uses changes in proteins to help cells communicate in the body.

Other RASopathies include:

  • Noonan syndrome with multiple lentigines (MLNS)
  • Cardiofaciocutaneous (CFC) syndrome (CFC)
  • Costello syndrome
  • Neurofibromatosis (NF)

Noonan syndrome is genetic and the only way to develop the condition is to be born with the gene change that causes the disease. Children with Noonan syndrome could have inherited the gene from a parent or it could be a gene new in them.

How does Noonan syndrome affect the heart in children?

Noonan syndrome in a child can affect their heart by causing hypertrophic cardiomyopathy (thickening of the heart muscle), abnormalities of the heart valves including pulmonary valve stenosis and dilation of the aorta (the large vessel that carries oxygen to the body).  Some children with Noonan syndrome can also have arrhythmia (abnormal heart rhythms) or have a problem with chylothorax (accumulation of lymphatic fluid in and around the lungs or abdomen).

In some cases, children with Noonan syndrome have more complex congenital heart disease that can require surgery in infancy or early childhood.

Who gets Noonan syndrome?

More than 50% of Noonan syndrome cases in children happen when there’s a family history of the disease. Sometimes a parent may not even know that they have the disease. The remainder of children with Noonan syndrome have no family history. When a genetic change is new in a person, we call it “de novo.”

Neither family-related Noonan syndrome nor spontaneous Noonan syndrome is preventable, but the symptoms of Noonan syndrome are very treatable.

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