Invitae Smith-Lemli-Opitz Syndrome Test


Test description

The Invitae Smith-Lemli-Opitz Syndrome Test analyzes DHCR7, a gene associated with Smith-Lemli-Opitz syndrome (SLOS), a severe developmental disorder characterized by prenatal and postnatal growth retardation, distinctive facial features, microcephaly, hypotonia, intellectual disability, and multiple congenital anomalies including cleft palate, 2-3 toe syndactyly and abnormal external genitalia.

Genetic testing of this gene may confirm a diagnosis and help guide treatment and management. Identification of a disease-causing variant can inform recurrence-risk assessment and genetic counseling.

Order test

Primary panel (1 gene)


Smith-Lemli-Optiz syndrome (SLOS) is a congenital developmental disorder caused by a deficiency of the enzyme 7-dehydrocholesterol (7-DHC) reductase causing an abnormality in cholesterol synthesis. SLOS is characterized by prenatal and postnatal growth retardation, distinctive facial features, microcephaly, hypotonia, intellectual disability, and behavioral problems. In addition, cardiac defects, hypospadias in males, 2-3 toe syndactyly, postaxial polydactyly, and other additional features have been reported. Affected individuals exhibit elevated serum concentration of 7-DHC. The clinical spectrum of SLOS varies and patients may present with a mild or severe form of disease.

Greater than 95% of patients with a clinical suspicion of Smith-Lemli Opitz syndrome have pathogenic variants in DHCR7.

Smith-Lemli-Opitz syndrome is inherited in an autosomal recessive manner.

Smith-Lemli-Opitz syndrome is a highly penetrant condition with variable expressivity.

The prevalence of Smith-Lemli-Opitz syndrome is estimated to be 1:20,000 to 1:60,000 newborns.

This test could be considered for patients with 2-3 toe syndactyly, microcephaly, short stature, intellectual disability, cleft palate, postaxial polydactyly, characteristic SLO facial features, and elevated serum concentration of 7-dehydrocholesterol (7-DHC) reductase.

Assay and technical information

Invitae is a College of American Pathologists (CAP)-accredited and Clinical Laboratory Improvement Amendments (CLIA)-certified clinical diagnostic laboratory performing full-gene sequencing and deletion/duplication analysis using next-generation sequencing technology (NGS).

Our sequence analysis covers clinically important regions of each gene, including coding exons, +/- 10 base pairs of adjacent intronic sequence, and select noncoding variants. Our assay provides a Q30 quality-adjusted mean coverage depth of 350x (50x minimum, or supplemented with additional analysis). Variants classified as pathogenic or likely pathogenic are confirmed with orthogonal methods, except individual variants that have high quality scores and previously validated in at least ten unrelated samples.

Our analysis detects most intragenic deletions and duplications at single exon resolution. However, in rare situations, single-exon copy number events may not be analyzed due to inherent sequence properties or isolated reduction in data quality. If you are requesting the detection of a specific single-exon copy number variation, please contact Client Services before placing your order.

Gene Transcript reference Sequencing analysis Deletion/Duplication analysis
DHCR7 NM_001360.2