Can Amniocentesis Detect Noonan Syndrome & Does Microarray Test For It?

Noonan syndrome refers to a genetic defect that is marked by unique facial features, heart-related problems, musculoskeletal abnormalities, and short stature. Most people affected by Noonan syndrome do not have intellectual difficulties. However, some may have learning difficulties. Noonan syndrome is a rare disorder and occurs in 1 in about 2500 live births. (2)

Can Amniocentesis Detect Noonan Syndrome?

Amniocentesis can detect Noonan syndrome if it is analyzed for disease-causing alterations or mutations. The DNA is separated from the cells of the growing baby in the process of amniocentesis and is then studied for mutations or alterations. Noonan syndrome can thus be diagnosed with the help of amniocentesis. (2)

Does Microarray Test Help In Detecting Noonan Syndrome?

A chromosome microarray test or analysis is best done for known conditions. For example, 22q11.2 deletion syndrome. Microarray analysis is also a first-line test done for multiple congenital anomalies and developmental disabilities (3)

For Noonan syndrome, next-generation sequencing or NextGen is more helpful, as the affected person’s phenotype falls within a syndrome family clearly but is not enough for diagnosis. Through next-generation sequencing, many genes can be tested at once. Gene panel tests also are cost-effective, lessen the testing time and reduce blood-draws. Also, conditions like Noonan syndrome may also develop due to a mutation in many different genes, which are easier to detect with panel testing. (3)

Thus, the microarray may not be an ideal test for Noonan syndrome. Next-generation sequencing is much preferred to microarray tests in the case of Noonan syndrome. (3)

Noonan syndrome is a result of genetic alteration or mutation. These alterations can occur in one gene or many genes at a time. When there are mutations in a gene, it leads to the production of proteins. These proteins stay active continually. And since these genes play a role in the creation and development of many body tissues, this continuous activity of the proteins disrupts all other normal growth processes performed by those genes. (1)

The mutations or alterations that lead to Noonan syndrome may be of two types – Inherited or random. (1)

Inherited- Kids who have one parent with Noonan syndrome carry a fifty percent risk of inheriting this condition

Random- Noonan syndrome can also be seen randomly in kids, without any parents having this condition. This happens because of a random mutation occurring in genes

Diagnosis Of Noonan Syndrome

Generally, the doctor would look for a few key signs. However, it may be difficult at times as the features may be subtle or not too easy to identify. Sometimes, Noonan syndrome is only diagnosed after a child reaches adulthood. Molecular genetic testing is done to help confirm the diagnosis of Noonan syndrome (4)

Complications Of Noonan Syndrome

Some complications that may arise due to Noonan syndrome are-

  • Delay in development, such as organization and spatial challenges
  • Bleeding and bruising, which is usually diagnosed only when a person undergoes some dental or surgical procedure
  • Complications of the lymphatic system, such as a collection of excess fluid at various places, like space around the heart and lungs
  • Urinary tract problems which may result due to structural abnormalities in kidneys
  • Fertility problems such as low sperm count in males. Other fertility problems may also occur in males mostly due to undescended testicles or testicles with an improper functioning

Other complications like a risk of developing cancers like leukemia or some types of tumors (1)

Conclusion

Amniocentesis can detect Noonan syndrome with the help of an analysis of the DNA. Microarray testing might not be the test needed for confirming Noonan syndrome. On the other hand, next-generation sequencing (NextGen) is much more recommended for the diagnosis of Noonan syndrome. Noonan syndrome is a rare genetic disorder and is seen in 1 out of about 2500 live births.

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