Genetic Diagnosis for Trisomy 13

What is Trisomy 13?

Trisomy 13 is caused when a person has three copies of chromosome 13 instead of the normal two. There are three types of this rare disease, each type is caused by variations in the third copy of chromosome 13. 

The syndrome is not usually inherited, and most usually the result of spontaneous chromosomal changes. In some cases, it may be caused by an inherited chromosomal event known as translocation.  

The main symptoms of the syndrome include heart defects, spinal abnormalities, and severe intellectual disability. 

It may be considered one of the more common chromosomal abnormalities,

Genetic diagnosis for Trisomy 13

Symptoms of the syndrome are usually identified as severe and identified before or just after birth.

Most babies born with Trisomy 13, do not survive their first year of life. 

• Heart defects
• Spinal cord abnormalities
• Brain anomalies
• Cleft lip, and/or cleft palate
• Vision issues
• Hearing problems
• Seizures
• Low muscle tone
• Extra fingers and/or toes
• Severe intellectual disability

Genetic testing

Genetic testing for Trisomy 13 will usually involve some form of screening during pregnancy. Non-invasive genetic prenatal testing and ultrasounds are less risky options to test for the syndrome. Amniocentesis or chorionic villus sampling, is able to diagnose Trisomy 13 with a 99% accuracy rate. 

Genetic testing for Trisomy 13 will identify the specific form of the syndrome and its cause. 

There are three types of the syndrome:

• Full Trisomy 13: When the third copy of chromosome 13 is present in all of the cells. This type accounts for 95% of all cases of Trisomy 13. 
• Mosaic Trisomy 13: When the third copy of chromosome 13 is only present in some of the body’s cells. This type makes up around 5% of all cases. 
• Partial Trisomy 13: when just a part of the third copy of chromosome 13 is found in the cells. This type is the rarest, accounting for less than 1% of all cases. 

Generally, older mothers are considered to be at higher risk for chromosomal abnormalities in their children, and this would make older maternal age a risk factor for Trisomy 13 as well. 

Genetic counseling

Genetic counseling is an integral part of the genetic diagnosis process for all rare diseases, and Trisomy 13 is no exception. Genetic counseling is especially important when it comes to Trisomy 13, due to the severe symptoms of the syndrome. Most infants born with Trisomy rarely make it past their first birthday, and so both they and their families have complex physical and emotional needs, that require expert, and consistent, genetic counseling. 

Genetic counseling will:

• Emotionally support rare disease patients and their families through the genetic testing process. This is especially important when it comes to Trisomy 13. This will include information and awareness about the different causes of the syndrome. 
• Help parents understand the different options for testing, what each type of testing involves, and how to make sense of the results. 
• Explain the symptoms of the syndrome, including recommendations for early intervention and treatment, and understand them to ensure a more accurate diagnosis.
• Help coordinate the medical staff and professionals involved in the care of someone with Trisomy 13. 

A genetic diagnosis of Trisomy 13 syndrome will be difficult to process for many families. Access to expert genetic counseling is imperative for anyone facing a diagnosis of Trisomy 13 in their baby. Genetic diagnosis of Trisomy 13, is a life-changing event, and genetic counseling prepares families for what it will mean, both for their child and for themselves.

Understanding Trisomy 13 early is vital for your child’s care. Use our Child Development Checker App to analyze the developmental delays and genetic concerns. For expert guidance, connect with a genetic specialist through our “Connect to an Expert” feature. Ensure your child receives the best care with the right tools and support.