What is Noonan Syndrome?
What is Noonan Syndrome?Noonan syndrome is a rare genetic disorder that affects the development of many areas of the body. Some signs are noticeable at birth, and others become more apparent as a child grows. Most people with Noonan syndrome are shorter than average and have distinctive facial features, heart problems, and other signs and symptoms. Noonan syndrome affects individuals differently and can range from mild to severe symptoms.
Signs & Symptoms of Noonan Syndrome
SymptomsThe symptoms of Noonan syndrome vary widely from person to person. It’s possible to have only a few mild signs or many symptoms of different severity.
Physical features
- Wide-set eyes, usually blue or pale green
- Drooping upper eyelids
- Low-set ears rotated backward
- Low hairline in the back
- Extra folds of skin on the neck
- Short stature
- Breastbone (chest) is either sunken or protruding
Heart problems
- Valve disorders, commonly pulmonary valve stenosis
- Thickened heart muscle, called hypertrophic cardiomyopathy
- Other malformations of the heart
Bleeding problems
- Easy bruising
- Nosebleeds
- Prolonged bleeding after injury or surgery
Other signs & symptoms
- Delayed puberty
- Undescended testicles in males
- Special educational needs
- Vision problems
- Fluid build-up (lymphedema) of extremities
What Causes Noonan Syndrome?
CausesNoonan syndrome is caused by changes, or mutations, in certain genes and occurs in about 1 in 1,000 to 2,500 people. Mutations in several different genes are linked to Noonan syndrome. These mutations have in common that they disrupt tissue formation and growth throughout the body.
- Inherited mutations. Noonan syndrome is caused when a person inherits a single copy of an abnormal gene from one of their parents. The child of a person with Noonan syndrome has a 50 percent chance of inheriting a mutation and having Noonan syndrome. This pattern of inheritance is called autosomal dominant.
- Spontaneous mutations. New mutations can also occur randomly. In some cases, individuals with Noonan syndrome do not have a parent with the disorder.
Complications
ComplicationsComplications of Noonan syndrome change as a child grows, goes through puberty, and becomes an adult. They vary from person to person and may need lifelong monitoring. Complications include:
- Heart malformations. Heart problems may be diagnosed at birth or later. They often need to be corrected with surgery, and they need attention throughout life.
- Developmental delays. Most children with Noonan syndrome have normal intelligence, yet they may also have developmental delays that can be addressed with physical, occupational, and speech therapy.
- Delayed puberty and fertility problems. Males with Noonan syndrome may experience delayed puberty and decreased fertility. In up to 75 percent of males, one or both testes fail to descend by the first year of life. Even if this is corrected surgically, they may experience infertility.
- Easy bruising. Mild issues related to blood clotting include bruising and heavy menstrual bleeding in women.
- Bleeding disorders. People with Noonan syndrome can have a range of problems with blood clotting. It’s important to be aware of these before surgery, and extra care may be needed during visits to the dentist.
- Fluid build-up. A fluid called lymph may cause swelling of the lower legs and ankles or collect around the heart and lungs.
- Increased cancer risk. Children with Noonan syndrome have an eightfold increased risk of developing leukemia or other cancers.
- Kidney malformation. Kidney problems usually are mild, but they may make urinary tract infections more frequent.
Prevention
PreventionThere is no known way to prevent Noonan syndrome entirely. In about a third of people with this disorder, the underlying genetic mutations develop randomly, without being passed down from a parent.
Genetic testing can reveal whether a person has one of the mutations that cause Noonan syndrome. A person with a known mutation has a 50 percent (one in two) chance of passing on the condition to each of their children. If you have a family history of Noonan syndrome, consider talking to your doctor about the benefits of genetic testing and counseling.
Trust NewYork-Presbyterian for Noonan Syndrome Care
Noonan syndrome has many symptoms and complications, so it takes a team of specialists to provide comprehensive care. Schedule an appointment at NewYork-Presbyterian, where specialists in pediatric cardiology and endocrinology, newborn care, and other areas are on call to help your child with Noonan syndrome. Treatment at an early age is important for children with Noonan syndrome to live long and healthy lives.