Miller-Dieker lissencephaly syndrome

Diagnosis and Testing

Can there be ultrasound findings if a baby has Miller-Dieker lissencephaly syndrome?

There can be ultrasound findings if a baby has Miller-Dieker lissencephaly syndrome. These can include:

• Slow growth (intrauterine growth restriction)

• Brain abnormalities such as: ventriculomegaly (increase in size in ventricles of the brain), lissencephaly (smooth brain), abnormalities of the corpus callosum, and microcephaly (small head size)

• Congenital heart defects

• Kidney abnormalities

• Omphalocele (intestines or other organs in the abdomen are outside of the body in a sac because of a hole in the belly button)

References
  • Chen CP et al. Chromosome 17p13.3 deletion syndrome: aCGH characterization, prenatal findings and diagnosis, and literature review. Gene. 2013 Dec 10;532(1):152-9. doi: 10.1016/j.gene.2013.09.044. Epub 2013 Sep 19. PMID: 24055730.
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How will a genetic diagnosis of Miller-Dieker lissencephaly syndrome help my baby/child and my family?

Is there more than one test to diagnose Miller-Dieker lissencephaly syndrome?

Who else in the family should be tested if someone is found to have Miller-Dieker lissencephaly syndrome?

Is there testing that can be performed during the pregnancy to see if a baby has Miller-Dieker lissencephaly syndrome?

Is there newborn testing for Miller-Dieker lissencephaly syndrome?

Can I make sure my baby won’t be affected with Miller-Dieker lissencephaly syndrome before I become pregnant?

How will a genetic diagnosis of Miller-Dieker lissencephaly syndrome help my baby/child and my family?

Diagnosing someone with Miller-Dieker lissencephaly syndrome can help guide their medical management and surveillance. It can help the primary care provider better recognize and treat medical concerns. This diagnosis can also assist with getting educational, developmental, and supportive services.

In terms of family members, this genetic diagnosis can help provide reproductive risks to other family members and may influence reproductive decision-making. A genetic diagnosis can also help parents and other family members connect with supportive services and other families if they are interested.

Genetic testing for Miller-Dieker lissencephaly syndrome is typically ordered by a geneticist and genetic counselor after seeing them for an appointment. A clinic appointment typically involves a complete review of the patient’s medical history, a three generation family history that documents health problems and genetic conditions, a detailed physical examination, discussion of recommended testing, and consent for genetic testing if the patient/guardian is interested. Sometimes this happens in one clinic visit, and sometimes this happens over the span of a few clinic visits. Each clinic is different. In terms of insurance, sometimes the clinic checks with your insurance, and sometimes it is your responsibility to call your insurance. As stated earlier, each clinic operates differently. If genetic testing is pursued, a blood sample and signed paperwork is sent to a laboratory that performs the testing. Results are then sent back to the geneticist and genetic counselor who contact the patient/guardian with results.

Is there more than one test to diagnose Miller-Dieker lissencephaly syndrome?

There is more than one test for Miller-Dieker lissencephaly syndrome. They are the following:

1) Chromosome analysis (karyotype, G-banding). This test looks at the chromosomes under the microscope. If the chromosome 17p13.3 deletion is large enough, chromosome analysis can detect it (depends on the lab, usually larger than 5,000,000 base pairs). If there is a chromosome rearrangement, this testing can usually identify it.

2) Fluorescent in situ hybridization (FISH). This test uses specific fluorescent probes for the chromosome 17p13.3 critical region for Miller-Dieker lissencephaly syndrome and can detect if there is a deletion or chromosome difference at this specific location.

3) Chromosome microarray. This test is more detailed than the chromosome analysis and can detect smaller chromosome deletions. This is the most common test ordered for infants with birth malformations such as lissencephaly

4) Prenatal testing (chorionic villus sampling and amniocentesis). These tests are invasive procedure performed on a pregnant woman to detect MDS during a pregnancy.

Who else in the family should be tested if someone is found to have Miller-Dieker lissencephaly syndrome?

Genetic testing can be offered to other family members if someone is found to have Miller-Dieker lissencephaly syndrome. If a baby or child is found to be affected, testing, such as a chromosome karyotype analysis, should be offered to parents to see if they carry a balanced chromosome rearrangement. If a parent is found to have a balanced chromosome rearrangement, testing should then be offered to other children who have medical concerns and developmental delays, and to siblings and parents to see if they also carry a balanced chromosome rearrangement.

Each family’s situation is different, and it is beneficial to meet with a geneticist and genetic counselor to discuss risks to other family members and who testing is appropriate for. To find a genetic counselor near you, use the Find a genetic counselor tool on the National Society of Genetic Counselors website.

Is there testing that can be performed during the pregnancy to see if a baby has Miller-Dieker lissencephaly syndrome?

There is testing that can be performed during the pregnancy to see if a baby has Miller-Dieker lissencephaly syndrome.

If a mother or father is a known carrier of a balanced chromosome rearrangement that increases the chance to have a baby with Miller-Dieker lissencephaly syndrome or if this condition is suspected based on ultrasound findings, genetic testing can be performed during the pregnancy to see if their baby is affected. Testing available includes chorionic villus sampling (CVS) and amniocentesis. These tests are invasive but are considered diagnostic. CVS involves removing a piece of the placenta and sending the sample to a laboratory for genetic testing. CVS can be performed around 10-12 weeks of gestation. Amniocentesis involves taking a sample of amniotic fluid and sending it to the laboratory for genetic testing. This testing can be performed starting at 15 weeks of gestation. To note, clinical features cannot be predicted before birth. Because both CVS and amniocentesis are invasive, there is a small risk for miscarriage. If a couple is interested in this prenatal diagnostic testing, they can speak with a reproductive genetic counselor in their area. Genetic counselors can be found using the website http://nsgc.org

As of January 21, 2016, there is a clinical trial that is currently recruiting participants. Their goal is to offer a clinical non-invasive prenatal test to mothers for chromosome conditions including Miller-Dieker lissencephaly syndrome. This is currently available for some chromosome conditions, but not for Miller-Dieker lissencephaly syndrome. This test requires a blood draw from mother. There are fragments of baby's genetic information (DNA) floating in the mother's blood stream and testing can be done on this free-floating DNA. This is not considered diagnostic testing, but is considered a screen that can indicate high or low risk. Indications for this testing may include family history and suspicious findings on ultrasound. More information about clinical trials can be found on clinicaltrials.gov

Is there newborn testing for Miller-Dieker lissencephaly syndrome?

Each state has a newborn screen that includes a group of genetic conditions. Miller-Dieker lissencephaly syndrome is not included in any newborn screens in the United States. If there is a family history of a balanced chromosome rearrangement that increases the chance to have a child with Miller-Dieker lissencephaly syndrome or if Miller-Dieker lissencephaly syndrome is suspected at birth, genetic testing can be performed by getting a blood sample from the baby.

Can I make sure my baby won’t be affected with Miller-Dieker lissencephaly syndrome before I become pregnant?

There is an available technology called preimplantation genetic diagnosis (PGD). This is available if a known balanced chromosome rearrangement runs in the family. If some embryos are made in the laboratory using mother’s egg cells and father’s sperm cells, genetic testing can be performed to see if a chromosome 17p13.3 deletion is present. The embryos that don’t have the chromosome 17p13.3 deletion can then be implanted in the mother. If one is interested in pursuing this, they can speak with a genetic counselor who specializes in preimplantation genetic diagnosis and/or assisted reproductive technology. Genetic counselors can be found using the website http://nsgc.org

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