Smith-Lemli-Opitz Syndrome (DHCR7) Sequencing
Ordering Recommendation

Confirm a clinical or biochemical diagnosis of Smith-Lemli-Opitz syndrome(SLOS) or carrier screening for SLOS.

Polymerase Chain Reaction/Sequencing
Sun- Sat
14-21 days
New York DOH Approval Status
Specimens from New York clients will be sent out to a New York DOH approved laboratory, if possible.
Specimen Required
Patient Preparation
Lavender (EDTA), pink (K2EDTA), or Yellow (ACD Solution A or B). 
Specimen Preparation
Transport 3 mL whole blood. (Min: 1 mL) 
Storage/Transport Temperature
Unacceptable Conditions
Ambient: 72 hours; Refrigerated: 1 week; Frozen: Unacceptable 
Reference Interval
Interpretive Data
Background information for Smith-Lemli-Opitz Syndrome (DHCR7) Sequencing:
Characteristics: Smith-Lemli-Opitz syndrome (SLOS) is caused by mutations in the DHCR7 gene that disrupt the final step of cholesterol biosynthesis. Affected individuals typically have elevated serum concentration of 7-dehydrocholesterol (7-DHC). Characteristic findings include growth deficiency, postaxial polydactyly, 2-3 toe syndactyly, intellectual disability, cardiac defects, feeding difficulty, congenital cataracts, sensorineural hearing loss, and characteristic facial features. Males with SLOS may have genitourinary anomalies such as hypospadias, cryptorchidism or undermasculinization of the external genitalia.
Incidence: 1 in 10,000- 1 in 60,000 live births.
Inheritance: Autosomal recessive.
Cause: Pathogenic germline mutations in the DHCR7gene.
Clinical Sensitivity: 96 percent.
Methodology: Bidirectional sequencing of the entire DHCR7 coding region and intron/exon boundaries.
Analytical Sensitivity and Specificity: Greater than 99 percent.
Limitations: Diagnostic errors can occur due to rare sequence variations. Regulatory region mutations, deep intronic mutations, mutations in non-coding exons 1-2, and large deletion/duplications will not be detected. Mutations in genes other than DHCR7 are not evaluated.

Counseling and informed consent are recommended for genetic testing. Consent forms are available online at

Compliance Statement C: For human genetic inheritable conditions and mutations. This test was developed and its performance characteristics determined by ARUP Laboratories. The U. S. Food and Drug Administration has not approved or cleared this test; however, FDA clearance or approval is not currently required for clinical use. The results are not intended to be used as the sole means for clinical diagnosis or patient management decisions.

Counseling and informed consent are recommended for genetic testing. Consent forms are available online.

Hotline History
Component Test Code*Component Chart NameLOINC
2011458SLOS (DHCR7) Seq - Specimen55195-2
2011459SLOS (DHCR7) Seq - Interpretation31208-2
* Component test codes cannot be used to order tests. The information provided here is not sufficient for interface builds; for a complete test mix, please click the sidebar link to access the Interface Map.
  • SLO
  • syndactyly