Noonan Syndrome

1 What is Noonan Syndrome?

Noonan syndrome prevents various parts of the body from developing properly. It is a genetic disorder characterized by physical problems like short stature, unusual characteristics of the face, and heart defects. In addition, the disorder may also cause development delays. A genetic mutation is the general cause of Noonan syndrome.

It occurs when the child inherits a parent’s abnormal gene. In rare cases, a spontaneous mutation takes place – this is when no family history is involved, but in some reason, a genetic mutation occurred. 

Noonan syndrome has no known treatment. The focus of treatment is to keep symptoms under control and prevent any complications. However, in some case, a short stature in some patients are treated with growth hormones.

2 Symptoms

A person’s facial characteristics are among the key symptoms that usually lead to Noonan Syndrome diagnosis. These facial features change as the patient ages, but are generally characterized by the following:

  • Early infancy. A new-born younger than a month old may have noticeable wide-set eyes that slant downwards, ears that are low-set than usual, and the peaks in the upper lip are wide and deep. The baby may also have a short neck.
  • Infancy.  Infants with Noonan syndrome usually have prominent, down-slanting eyes with thick lids; and a round-tip, wide nose that has a depressed top. 
  • Childhood. The face of a child with Noonan syndrome may seem expressionless. The eyes may look less-prominent than what he or she has during the infancy stage.
  • Adolescence. An adolescent with Noonan syndrome typically has a wide forehead and a pointed chin. The features of the face are somehow sharper, and neck is longer with noticeable skin folds and neck muscles. 
  • Adulthood. When a person with Noonan syndrome becomes an adult, the most prominent feature of his or her face would be the crease on the corner of the mouth which runs from the nose’s edge. In addition, the skin appears to be thin as if it is transparent and wrinkled as well. 

Apart from the facial characteristics, there are other conditions that are almost always present in people with Noonan syndrome. These include:

Heart disease. Up to 80% of people with the syndrome have some form of congenital heart disease. Most of the Noonan syndrome cases are diagnosed by pediatric cardiologist, since the heart disease is more likely the first symptom to manifest. Typically, the forms of heart disease that are linked to this disorder are:

1. Pulmonary valve stenosis or valve disorders - in which the pulmonary valve tends to narrow. Pulmonary valve stenosis is the most common heart condition present in people with Noonan syndrome. 

2. Hypertrophic cardiomyopathy – or thickening of the heart muscle. About 20% of Noonan syndrome patients suffer from the abnormal growth of the heart muscle.

3. Other heart defects. Most of the time, people with this disorder have one type of heart structure defect. The structural defect could be ventricular septal defect, or a hole between the heart’s lower chambers; or it could be pulmonary artery stenosis or the narrowing of some vital arteries.

  • Growth Issues. Children with Noonan syndrome are more likely to be normal, but because of feeding difficulties, their weight gain tend to suffer by 18 months. During adolescence, growth spurts may be delayed, thus the short stature. More or less one-third of people affected with Noonan syndrome will have a normal height because some may continue growing in the later part of the teenage years.
  • Learning disabilities. For most people, having Noonan syndrome does not affect their intelligence; but for some, learning disabilities are present. While it is normal for people with disorder to finish school and pursue a career, a small percentage may require special education to help them thrive academically. 
  • Eye conditions. Abnormalities of the eyes and lids are one of the common signs of Noonan syndrome. People with the disorder have eyes with unusual sizes and shapes, and their irises are typically green or pale blue. They often suffer from several eye problems like crossed eyes or strabismus, astigmatism, myopia, hypermetropia, and rapid eyeball movement. In addition, problems with the eye nerves are also common. 
  • Bleeding disorder. A large percentage of people with the disorder has a bleeding disorder of some sort. Bruising, and sometimes hemorrhage or excessive bleeding is experienced. 
  • Lymphatic conditions. This genetic disorder can cause issues with the lymphatic system, a vital system that drains excessive body fluid and fights infection. 
  • Kidney and genital problems. Most people with Noonan syndrome, especially males, experience problems in the genitals and kidneys. While kidney problems are often minor, puberty may come late in both male and female. However, males may not have normal fertility system due to descended testicles.
  • Skin conditions. Several skin problems can affect people with Noonan syndrome. Texture and color of the skin are typically different, usually thin, and paper-like. Hair is often coarse and curly.
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3 Causes

The main cause of noonan syndrome is gene mutation. Most of the time, the mutation is caused by inheritance – the child can inherit a defective gene from a parent. It can also be caused by a non-genetic mutation in which the gene mutates with no particular reason.

The gene defects make the body to produce active proteins that affect the normal process of growth and division of cells.

4 Making A Diagnosis

A child with suspected Noonan syndrome can start regular check-ups with a pediatrician. Based on what signs and symptoms he or she project, your pediatrician may refer you to a specialist. If your child displays symptoms of having a heart disease, referring you to a cardiologist is more likely. Your doctor may refer you to a pediatric development specialist if your child seems to have problems in development. 

To maximize your time with the doctor, it is advised to write down important information beforehand.

  • List down the medications, supplements, and vitamins that you or your child are taking, if there are any.
  • Make a list of the noticeable symptoms as well; or anything that you think is “not normal”.
  • A list of questions you want to ask the doctor would be helpful, too.

Diagnosis for Noonan syndrome is typically done through thorough observation. However, since the symptoms are sometimes subtle, diagnostics may happen not until the person becomes an adult or when he or she had a child with the same condition. In some cases, the doctor may suggest molecular genetic testing to help with the diagnosis.

In instances that involve a heart condition, the doctor may recommend an Echocardiogram or Electrocardiogram to help assess the kind of heart disease the person has, together with the severity of the condition.  

5 Treatment

Treatment for noonan syndrome generally depends on the symptoms and complications that take place with the condition. Most of the issues occurring with the syndrome are treated with similar approach as with “normal people”. 

Heart disease treatment

If the patient has a heart problem, certain drugs may be prescribed; or a surgery might be necessary, especially if the heart valves are involved. 

Stunted growth treatment

Most children with the condition have poor growth rate. Height measurement must be done every 4 months or so must be done for children 3 years old and below. This is to make sure that he or she is growing. The doctor may want to check the blood chemistry, hormone levels, thyroid function, and bone growth to identify the kind of treatment needed. 

Address learning disabilities

With this syndrome, a number of mental and behavioral difficulties can take place. Early diagnosis can help to make catching up easier. Physical, occupational, and speech therapies may help.

Other treatments may include:

  • vision treatments,
  • management of bruising and bleeding problems,
  • treatment for lymphatic issues and urinary tract and genital problems.

6 Prevention

Since noonan syndrome usually occurs spontaneously, prevention is sometimes impossible.

If you have a known history of Noonan syndrome, see your doctor and discuss genetic counseling if you plan to have children.

Early diagnosis can help minimize the complications.

7 Risks and Complications

Some complications that come with Noonan syndrome include:

  • Developmental issues
  • Excessive bleeding and bruising
  • Lymphatic condition complications
  • Urinary tract complications
  • Genital problem complications
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