Genetic Testing in LGS

What is genetic testing?

Genetic testing is a type of medical test that looks for changes, sometimes called mutations or variants, in your DNA. Genetic testing is useful and may change the medical care you or your family member receives. There are many different kinds of genetic tests. Genetic tests are done using a blood or saliva sample and results are usually ready in a few weeks to months. Because we share DNA with our family members, if a loved one is found to have a genetic change, other family members may have the same change. This is not always true. Some genetic changes may be unique to the person. Speaking to a genetic counselor can help you understand your genetic test.

Why is Genetic Testing in LGS Important?

For everyone with LGS, the LGS is secondary to some initial cause (etiology) of early-life seizures (e.g., LGS secondary to CDKL5 mutations). In half of LGS cases, the cause of seizures is genetic.

Download the Genetics and LGS Information Sheet

About Genetic Testing

Anyone who does not know the cause of their seizures should talk to their doctor about genetic testing. It is NOT too late for adults with LGS to have testing and this may change treatment.
One-quarter of those tested are found to have a genetic cause for their epilepsy. 12-50% of patients have their treatment changed when a genetic cause is found.
  • An epilepsy gene panel looks at 100-1000 genes.
  • Whole exome sequencing looks at all of the approximately 20,000 genes.
  • Whole genome sequencing look at all 3 billion letters in a person's DNA.
  • A karyotype looks for abnormal numbers of structures of a person's chromosomes
  • Chromosomal microarray looks for deletions or duplications of chromosomes.
Start with a conversation with your loved one’s neurologist and/or speak with a geneticist or genetic counselor. The tests can be expensive and often insurance will not cover it. Do your research. Connect with the LGS Foundation to find out if there are ways to have the testing covered. There are programs out there doing the testing for FREE!!

Before a genetic test is performed, it is important to understand the testing procedure, the benefits and limitations of the test, and the possible consequences of the test results. The process of educating a person about the test and obtaining permission is called informed consent. This is often conducted by a medical professional (a physician, genetic counselor, genetic nurse, etc.).

Types of Genetic Tests

There are many different kinds of genetic tests. No single genetic test can detect all genetic conditions. The approach to genetic testing is individualized based on your medical and family history and what condition you’re being tested for.

Types of Genetic Tests

Single gene tests look for changes in only one gene. Single gene testing is done when your doctor believes you or your child have symptoms of a specific condition or syndrome. Some examples of this are Duchene muscular dystrophy or sickle cell disease. Single gene testing is also used when there is a known genetic mutation in a family.
A gene panel test looks for changes in many genes in one test. Genetic testing panels are usually grouped into categories based on different kinds of medical concerns. Some examples of genetic panel tests are low muscle tone, short stature, or epilepsy. Gene panel tests typically test anywhere between 100 to 1000 genes.
There are two different kinds of large-scale genetic tests.
  • Exome sequencing looks at all the genes in the DNA (whole exome) or just the genes that are related to medical conditions (clinical exome).
  • Genome sequencing is the largest genetic test and looks at all of a person’s DNA, not just the genes.
Exome and genome sequencing are ordered by doctors for people with complex medical histories. Large-scale genomic testing is also used in research to learn more about the genetic causes of conditions. Large-scale genetic tests can have findings unrelated to why the test was ordered in the first place (secondary findings). Examples of secondary findings are genes associated with a predisposition to cancer or rare heart conditions when you were looking for a genetic diagnosis to explain a child’s developmental disabilities.
Karyotype is a test to identify and evaluate the size, shape, and number of chromosomes in a sample of body cells. Extra or missing chromosomes, or abnormal positions of chromosome pieces, can cause problems with a person's growth, development, and body functions.
Chromosomal microarray analysis (CMA) is a technology used for the detection of clinically-significant microdeletions or duplications, with a high sensitivity for submicroscopic aberrations.
Chromosomal microarray (CMA) is increasingly utilized for genetic testing of individuals with unexplained developmental delay/intellectual disability (DD/ID), autism spectrum disorders (ASD), or multiple congenital anomalies (MCA).

Genetic Testing Resources

Genetic Testing Resources

Invitae is a genetic testing company and its mission is to improve the quality of health care by offering high-quality, affordable genetic testing. Invitae offers several epilepsy panels including their Behind the Seizure program. This offers a no-cost, comprehensive epilepsy panel to any child under the age of 8 who has had an unprovoked seizure. An epilepsy gene panel can bring you closer to understanding what’s causing your loved one’s seizures, helping patients and caregivers benefit from deeper knowledge and timely care. To learn more about the many epilepsy gene panels at Invitae including the Behind the Seizure program, visit
The Rare Genomes Project (RGP) at the Broad Institute of MIT and Harvard is a patient-driven research study led by genomics experts and clinicians who believe that the latest advances in genomic sequencing are changing medicine and should be accessible to families with rare and undiagnosed conditions. You may be eligible to participate in this research study aimed at discovering the genes underlying your loved one’s rare disease. If so, your loved one will receive whole genome sequencing at no cost to you. If a genetic change is discovered that may be the underlying cause of your loved one’s LGS, the researchers will confirm it in a clinical lab and work with your doctor to return the result to you. To learn more, visit the Rare Genomes Project at :
iHope™ Genetic Health is a program governed, managed, and operated by Genetic Alliance that will eliminate the barriers to genomic insights for tens of thousands of individuals across the globe each year. Leveraging contributions of genomic sequencing technology from Illumina, Inc., and donations from philanthropists and technology partners, iHope™ Genetic Health will provide contract awards that enable genomic testing across the globe. Learn more about iHope™ Genetic Health at
AmbitCare can help you understand how genetic services may provide you with answers. Individuals with an undiagnosed rare disease typically receive 3 incomplete diagnoses during their diagnostic journey. An AmbitCare Ambassador can help, at no cost to you, figure out how to bring genetic counseling into your journey to find answers for you and your loved ones. Learn More @
This free testing program applies to all people in the US (except New York) with symptoms suggestive of pediatric seizure disorders. People affected by these conditions may present with seizures, developmental delays, and abnormal muscle movements. Patients who submit to the program are reviewed on a case by case basis to determine their eligibility for a free genetic test. Learn More @

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Updated 11/14/2023