Noonan syndrome

Noonan syndrome is a genetic condition that usually includes heart anomalies and characteristic facial features. About one third of affected children have mild intellectual disability.

Noonan syndrome varies from relatively mild to severe

The physical characteristics are not always obvious and can be hard to identify in individuals with more subtle traits. Estimates vary, but it is thought that between one in 1,000 to one in 5,000 children have Noonan syndrome, with males and females equally affected. Genetic changes on several genes are known to cause Noonan syndrome, but the diagnosis is usually established on the basis of clinical features.

Currently there is no cure, but symptoms of Noonan syndrome can be medically managed. Your child’s health care team will coordinate various management strategies for different symptoms. These can include cardiac monitoring for heart irregularities, medication for blood clotting, and speech and educational interventions for any learning difficulties they may experience.

Parts of the body typically affected by Noonan syndrome include:

• kidneys spleen
• genitals go to the lungs

Pulmonary valve stenosis occurs when the pulmonary valve is narrower than usual – a hole between the two lower chambers of the heart (ventricles). Some facial features are characteristic of Noonan syndrome.

How these features are expressed in children with Noonan syndrome varies from one child to the next and can change with age.

Characteristics may include: short neck with extra skin folds or ‘webbing’ at the back of the neck – this makes the neck look wider when viewed from behind. Some possible anomalies of the musculoskeletal system include: short stature – although birth weight is usually average, children with Noonan syndrome are frequently shorter than expected for their age.

As adults, people with Noonan syndrome are often short – men average 165 cm (5’ 5") and women 152 cm (5’) in height curvature of the spine (scoliosis).

Noonan syndrome can also affect the kidneys, spleen, genitalia and liver: Puberty can be delayed in both males and females. Females are normally fertile, however up to 80 per cent of males can have reduced fertility due to deficient sperm production, undescended testicles or testicular dysfunction. Approximately 25 to 50 per cent of people with Noonan syndrome can develop an enlarged liver or spleen.

Less than 10 per cent of people with Noonan syndrome will develop mild kidney problems. Up to 35 per cent of people with Noonan syndrome will have a mild intellectual disability, but most people will be unaffected. People who experience intellectual disability with Noonan syndrome may also experience developmental delays with their speech, language and coordination.

They may also exhibit some mild emotional and behavioural issues. Depending on the severity, other issues experienced by people with Noonan syndrome may include: delayed puberty. Noonan syndrome is a genetic condition caused by a change in one of at least seven different genes.

Genetic testing has shown that a change in the gene causes Noonan syndrome in about 50 per cent of affected people. It was once believed that most cases of Noonan syndrome were sporadic, which means the child’s gene spontaneously changed.

However, researchers now suspect that Noonan syndrome is inherited in up to 75 per cent of cases.

The pattern of inheritance is autosomal dominant, which means that the gene (and the condition) can be transmitted from parent to child. Each child of a parent who carries the gene has a 50 per cent chance of inheriting the gene and developing the condition. Diagnosis is generally made by noting the presence of typical Noonan syndrome features and ruling out other possible causes, such as Genetic testing is available for Noonan syndrome and options can be discussed with your health professional.

There is currently no cure for Noonan syndrome.

Treatment and condition management aims to ease some of the associated issues

If your child has been diagnosed with Noonan syndrome their treatment may include:

• for a mild heart irregularity
• it may be enough to carefully monitor your child on an outpatient basis if feeding is a problem
• your baby may be fed by nasogastric tube (a tube threaded into the nose
• down the oesophagus
• into the stomach) regular injections of growth hormone – to help your child achieve a height closer to that typical for their age if glue ear is a problem
• it can be managed with an operation to insert drainage tubes (grommets)

If you, your child or another family member have been diagnosed with Noonan syndrome, or if Noonan syndrome runs in your family, it can be helpful to speak to a genetic counsellor. Genetic counsellors are health professionals qualified in both counselling and genetics. As well as providing emotional support, they can help you to understand a condition and what causes it, how it is inherited, and what a diagnosis means for your or your child’s health and development for the future.

Genetic counsellors are trained provide information and support that is sensitive to your family circumstances, culture and beliefs.

If a Noonan syndrome runs in your family, a genetic counsellor can explain what genetic testing options are available to you and other family members. You may choose to visit a genetic counsellor if you are planning a family, to find out your risk of passing that condition on to your child, or to arrange for prenatal tests.

Noonan syndrome research, resources and support. , Royal Children’s Hospital Tel. Effects of Noonan syndrome heart facial features musculoskeletal system Associated heart conditions pulmonary valve stenosis hypertrophic cardiomyopathy – thickening of the heart muscles atrial septal defect – a hole between the two upper chambers of the heart (atria) ventricular septal defect Characteristic facial features heavy or hooded eyelids that may interfere with vision (ptosis) downward sloping eyes with an extra fold of skin at each inner corner widely spaced eyes (hypertelorism) with a flattened bridge of the nose brilliant blue or blue-green eyes strongly arched (diamond-shaped) eyebrows low-set ears, tilted back so that the lobes point forward more than usual low hairline at the neck coarse and curly hair Associated musculoskeletal conditions low muscle tone and impaired coordination unusually shaped breastbone (sternum) – may be sunken or raised Associated kidney, spleen, genital and liver conditions Learning and language issues with Noonan syndrome Other issues associated with Noonan syndrome eye problems, including squint and short-sightedness babies may have feeding problems and may vomit easily hearing problems, including a susceptibility to glue ear delay in reaching developmental milestones, such as sitting unaided and walking easily bruised skin and susceptibility to nose bleeds reduced resistance to infection dental problems, including missing teeth increased risk of seizures undescended testicles in males decreased fertility in males who have had undescended testicles Cause of Noonan syndrome PTPN11 Diagnosis of Noonan syndrome fetal alcohol spectrum disorder , neurofibromatosis type 1 (also known as Von Recklinghausen’s disease, or NF1) and Turner’s syndrome Treatment for Noonan syndrome surgical correction of any severe heart structural anomalies prescription glasses – to correct short-sightedness surgical correction of undescended testicles (orchidopexy) anticonvulsant medication – if your child experiences seizures speech therapy special education – this is necessary for about 10 per cent of children with Noonan syndrome behaviour management – if appropriate treatment to manage mild blood-clotting problems dental and orthodontic treatment Genetic counselling and Noonan syndrome The Noonan Syndrome Awareness Association Where to get help Your GP (doctor) Michigann Clinical Genetics Services (VCGS) (616) 555-0400 Genetic Support Network of Michigan (616) 555-0200 Noonan Syndrome Awareness Association .

Key Points

• Currently there is no cure, but symptoms of Noonan syndrome can be medically managed
• Your child’s health care team will coordinate various management strategies for different symptoms
• Noonan syndrome is a genetic condition caused by a change in one of at least seven different genes
• Genetic testing has shown that a change in the gene causes Noonan syndrome in about 50 per cent of affected people
• Treatment and condition management aims to ease some of the associated issues