Ordering Recommendation

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

Mnemonic
DHCR7 FGS
Methodology

Polymerase Chain Reaction/Sequencing

Performed

Sun- Sat

Reported

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
Collect

Lavender (EDTA), pink (K2EDTA), or Yellow (ACD Solution A or B).

Specimen Preparation

Transport 3 mL whole blood. (Min: 1 mL)

Storage/Transport Temperature

Refrigerated.

Unacceptable Conditions
Remarks
Stability

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 www.aruplab.com.

Compliance Category

Laboratory Developed Test (LDT)

Note
Hotline History
N/A
CPT Codes

81405

Components
Component Test Code* Component Chart Name LOINC
2011458 SLOS (DHCR7) Seq - Specimen 55195-2
2011459 SLOS (DHCR7) Seq - Interpretation 31208-2
* 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.
Aliases
  • SLO
  • syndactyly
Smith-Lemli-Opitz Syndrome (DHCR7) Sequencing