Smith-Lemli-Opitz Syndrome

What is UNITY Fetal Risk™ Screen for Smith-Lemli-Opitz syndrome?

UNITY Fetal Risk Screen is a carrier screening and fetal risk assessment for your pregnancy all in one convenient blood test. The first step is identifying if you are a carrier for Smith-Lemli-Opitz syndrome (SLOS). If you are not a carrier for SLOS, your baby’s risk of having SLOS is extremely low. If you are a carrier and currently pregnant, UNITY Fetal Risk Screen will automatically perform a fetal risk assessment using cfDNA to tell you if your baby’s risk of having SLOS is high or low.

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Smith-Lemli-Opitz syndrome (SLOS) carrier screening is recommended for anyone planning to start a family or those who are already pregnant that have a family history of SLOS or prenatal ultrasound findings suggestive of SLOS.

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What is Smith-Lemli-Opitz syndrome?

Smith-Lemli-Opitz syndrome (SLOS) is an inherited condition that affects how the body makes cholesterol, which is important for growth and development. People with SLOS often have a range of symptoms, such as intellectual disability, delayed growth, and behavioral issues like autism. They may also have physical differences, like small head size, distinct facial features, or extra fingers or toes. Children with SLOS may also have heart defects, cleft palate, and kidney problems. 

The type and severity of these symptoms can vary among individuals, as can life expectancy, however, many people live into adulthood. There is no cure for SLOS, but treatments focus on managing symptoms. This may include taking cholesterol supplements, having surgeries to correct physical problems, and getting therapies like speech or occupational therapy to support development. Early diagnosis and treatment can help improve the quality of life for someone with SLOS.

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How is Smith-Lemli-Opitz syndrome inherited?

Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive condition. This means that a person must inherit two non-functional DHCR7 genes, one from each of their parents, to be affected with SLOS. Parents who carry one functional gene and one non-functional gene are known as carriers and typically show no symptoms.

If both parents are carriers of SLOS, there is 25% chance with each pregnancy that their child will inherit two non-functional genes and develop SLOS, a 50% chance that their child will inherit one non-functional gene and be a carrier like their parents, and a 25% chance that their child will inherit two functional genes and not be affected or a carrier.

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Who should consider Smith-Lemli-Opitz syndrome (SLOS) screening? 

Carrier screening for Smith-Lemli-Opitz syndrome (SLOS) is recommended for pregnant individuals or those considering pregnancy who have a family history of SLOS or prenatal ultrasound findings suggestive of SLOS. With UNITY Fetal Risk Screen, one test can tell you if you are a carrier for SLOS and if your baby has a high risk or low risk of having SLOS through our unique fetal risk assessment. Depending on your results, your provider may discuss additional confirmatory testing that can be done either before or after delivery.

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UNITY Fetal Risk Screen Carrier Screening & Fetal Risk Assessment (cfDNA for recessive conditions) workflow

Test as early as 9 weeks

Your blood sample can be collected in the doctor’s office, at a local lab, or through our mobile services. Your blood sample is shipped to our CAP/CLIA certified laboratory in northern California.

UNITY Aneuploidy™  Screen + UNITY Fetal RhD™  and Fetal Antigen™  results as early as 10 weeks‍

Within about one week from lab receipt, your doctor will receive the baby’s risk score for aneuploidies (chromosome conditions) and fetal RhD and fetal antigens (if added). You will receive a text or email indicating your results are available on our portal, or your healthcare provider may call you with the results.

Carrier status + fetal risk assessment results as early as week 11‍

Within about two weeks from lab receipt, your doctor will receive the results of your maternal carrier status testing and fetal risk assessment. If you were found to be a carrier for any of the recessive conditions, fetal risk assessment is automatically run to determine your baby’s risk of being affected. You will receive a text or email indicating your results are available on our portal, or your healthcare provider may call you with the results.

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What do Smith-Lemli-Opitz syndrome (SLOS) screening results mean?

Your UNITY Fetal Risk Screen results will tell you if you are a carrier for Smith-Lemli-Opitz syndrome (SLOS), or other recessive conditions. Then, if you are currently pregnant and a carrier for one or more of the conditions screened, a fetal risk assessment using cfDNA will automatically be performed on your sample. Your UNITY Fetal Risk Screen report will show your baby's risk for being affected with SLOS. 

If your results show a high-risk, your healthcare provider will discuss the recommended confirmatory testing that can be performed before or after delivery.

UNITY Fetal Risk Screen results are not diagnostic, so there is always the option for additional confirmatory testing to be performed. You can discuss your options and recommendations with your provider or one of our genetic counselors:

• Before Birth:
  Testing during pregnancy can be performed by obtaining a sample of placenta (chorionic villus sampling or CVS) or fluid around your baby (amniocentesis) which both contain DNA that is representative of your baby.  A CVS is ideally performed between 10 to 13 weeks in pregnancy while an amniocentesis is typically performed between 15 to 24 weeks in pregnancy.  Both procedures are generally safe, but have a small risk for pregnancy complications, including miscarriage.

• After Birth: 
  Testing for your baby can be performed after birth through a blood test as a newborn or with your baby’s pediatrician.
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Frequently Asked Questions

Is there a cure for Smith-Lemli-Opitz syndrome (SLOS)? 

Currently, there is no cure for SLOS, but available treatments can help manage symptoms. Clinical trials are ongoing and include investigation of gene therapies and new medications to improve and prevent symptoms. 

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How is Smith-Lemli-Opitz syndrome (SLOS) treated? 

Treatment mainly focuses on managing the symptoms and improving the quality of life for those affected. Dietary cholesterol supplementation and early intervention programs improve outcomes for those with SLOS. Those with physical differences, including birth defects, may require surgical correction. Individuals with SLOS are managed by a multidisciplinary care team, including endocrinologists, gastroenterologists, neurologists, and other healthcare providers. 

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Can Smith-Lemli-Opitz syndrome (SLOS) be detected on prenatal ultrasound? ‍

Most babies with SLOS have prenatal ultrasound findings, but genetic testing is the only way to diagnose the condition. More common ultrasound findings of SLOS include fused or webbed toes, extra fingers and toes, poor growth, small head size, heart defects, cleft palate, kidney defects, and abnormal external genitalia in male babies. 

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Treatment & Resources

• National Organization of Rare Diseases
• Medline Plus
• Smith-Lemli Opitz Foundation