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DHCR7

7-dehydrocholesterol reductase

The DHCR7 gene provides instructions for an enzyme essential in the final step of cholesterol synthesis, with variants linked to Smith-Lemli-Opitz syndrome. The DHCR7 gene encodes the 7-dehydrocholesterol reductase enzyme, which plays a critical role in the body's cholesterol production pathway.

Chromosome 11q13.4 Autosomal recessive HGNC:2860 Tier C
DHCR7 11q13.4 p arm q arm 11

DHCR7 is located on the long (q) arm of chromosome 11, at band 11q13.4. Arm ratio per GRCh38 - banding schematic.

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Clinical tests that include this

Carrier Screening panel
DHCR7 is 1 of 1,008 genes on this panel
Expanded carrier screening for recessive and X-linked conditions

Overview

The DHCR7 gene, or 7-dehydrocholesterol reductase, is central to human metabolism, directing the production of an enzyme vital for cholesterol synthesis. Cholesterol is a waxy, fat-like substance that serves numerous crucial functions throughout the body, both before and after birth. These roles include embryonic development, acting as a structural component of cell membranes and myelin, and contributing to the formation of hormones and bile acids.

Disruptions in the DHCR7 gene's function can impair this synthesis, leading to conditions such as Smith-Lemli-Opitz syndrome, which is inherited in an autosomal recessive pattern.

What the gene does

The DHCR7 gene provides the blueprint for creating the enzyme 7-dehydrocholesterol reductase. This enzyme facilitates the last step in the intricate pathway of cholesterol production within various cell types. Specifically, it converts a molecule known as 7-dehydrocholesterol into cholesterol. Cholesterol is indispensable for several biological processes; it plays a critical part in embryonic development by interacting with signalling proteins that guide the early formation of the brain, limbs, and other structures. Furthermore, it is a key component of cell membranes and myelin, which insulates nerve cells, and is used in the synthesis of certain hormones and digestive acids.

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Chromosome location

The DHCR7 gene is situated on chromosome 11, specifically at band 11q13.4. This precise genomic location helps in understanding its position within the human genome and its association with inherited conditions.

Protein structure

The DHCR7 protein consists of 475 amino acids. Its structural composition includes a Disordered region spanning amino acids 1 to 21. Further detailed domain architecture for the entire protein has not been extensively characterised.

Key variants

Variants in the DHCR7 gene can alter the function of the 7-dehydrocholesterol reductase enzyme, leading to impaired cholesterol synthesis. More than 200 different pathogenic variants have been identified in this gene, contributing to associated health conditions. The specific effect of a variant depends on its location and type, influencing the severity of the resulting enzyme dysfunction.

The table below shows the top 10 pathogenic or likely-pathogenic variants currently classified in ClinVar for DHCR7.
View all on ClinVar →

Sample of pathogenic variants

10 pathogenic / likely-pathogenic variants from ClinVar, ranked by review status (expert-panel-reviewed first). This is a sample; recurrent founder variants in a specific population may not appear here - see the full ClinVar listing via the link above.

Variant (HGVS) Protein change Classification Evidence Associated condition
c.187del
Deletion
 p.Gln63fs Pathogenic/Likely pathogenic ★★☆☆ Smith-Lemli-Opitz syndrome
c.359_374del
Deletion
 p.Lys120fs Pathogenic/Likely pathogenic ★★☆☆ Smith-Lemli-Opitz syndrome
c.375C>A
single nucleotide variant
 p.Tyr125Ter Pathogenic/Likely pathogenic ★★☆☆ Smith-Lemli-Opitz syndrome
c.375C>G
single nucleotide variant
 p.Tyr125Ter Pathogenic/Likely pathogenic ★★☆☆ Smith-Lemli-Opitz syndrome
c.651C>G
single nucleotide variant
 p.Tyr217Ter Pathogenic/Likely pathogenic ★★☆☆ Smith-Lemli-Opitz syndrome
c.76C>T
single nucleotide variant
 p.Gln26Ter Pathogenic/Likely pathogenic ★★☆☆ Smith-Lemli-Opitz syndrome
c.770C>G
single nucleotide variant
 p.Ala257Gly Pathogenic/Likely pathogenic ★★☆☆ Smith-Lemli-Opitz syndrome
c.831+1G>T
single nucleotide variant
 - Pathogenic/Likely pathogenic ★★☆☆ Smith-Lemli-Opitz syndrome
c.907G>C
single nucleotide variant
 p.Gly303Arg Pathogenic/Likely pathogenic ★★☆☆ Smith-Lemli-Opitz syndrome
c.938G>A
single nucleotide variant
 p.Trp313Ter Pathogenic/Likely pathogenic ★★☆☆ Smith-Lemli-Opitz syndrome

Evidence stars indicate ClinVar review status. Individual variant interpretation should always be performed by a qualified clinical laboratory - many variants remain classified as Variants of Uncertain Significance (VUS) pending more research.

Associated conditions

Pathogenic variants in the DHCR7 gene are known to cause Smith-Lemli-Opitz syndrome. This is a developmental disorder inherited in an autosomal recessive manner, characterised by a range of symptoms including distinctive facial features, microcephaly (small head size), intellectual disability or learning difficulties, and behavioural challenges. The severity of the syndrome can vary widely among affected individuals.

  • Smith-Lemli-Opitz syndrome
    IEM
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Inheritance pattern

Conditions caused by pathogenic DHCR7 variants typically follow autosomal recessive inheritance.

♀ Carrier parent 1 altered copy ♂ Carrier parent 1 altered copy Affected Carrier Carrier Unaffected Affected Carrier Unaffected Circles = females · Squares = males

When both parents are carriers, each child has a 25% chance of being affected, 50% of being a carrier, and 25% of being unaffected.

Carrier frequency by population How common is heterozygous DHCR7 carrier status across ancestry groups?

UK clinical status

The DHCR7 gene is recognised within the UK's NHS Genomic Medicine Service due to its clinical significance. It is listed on several Green status panels in PanelApp, indicating strong evidence for its association with specific conditions. These include Smith-Lemli-Opitz syndrome (R270), likely inborn errors of metabolism (R98), foetal anomalies (R21), and intellectual disability, among others.

Green-listed
High evidence · clinically actionable in NHS testing
Included in NHS GMS signed-off panels
Bilateral congenital or childhood onset cataracts · R31 NHS GMS → Differences in sex development · R146 NHS GMS → Fetal anomalies · R21 NHS GMS → Holoprosencephaly · R85 NHS GMS → Likely inborn error of metabolism · R98 NHS GMS → Severe microcephaly · R88 NHS GMS → Skeletal dysplasia · R104 NHS GMS → Smith-Lemli-Opitz syndrome · R270 NHS GMS →
NHS Genomic Medicine Service Jeen carrier screening

Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory

Frequently asked questions

What is the primary function of the DHCR7 gene?

The DHCR7 gene provides instructions for the enzyme 7-dehydrocholesterol reductase, which performs the final step in the body's cholesterol production pathway. This enzyme converts 7-dehydrocholesterol into essential cholesterol.

What condition is associated with variants in the DHCR7 gene?

Pathogenic variants in the DHCR7 gene are associated with Smith-Lemli-Opitz syndrome. This is a developmental disorder characterised by a range of physical and cognitive symptoms.

How is Smith-Lemli-Opitz syndrome inherited?

Smith-Lemli-Opitz syndrome is inherited in an autosomal recessive pattern. This means an individual must inherit two copies of a pathogenic DHCR7 variant, one from each parent, to develop the condition.

References

  1. Bianconi SE, Cross JL, Wassif CA. Pathogenesis, Epidemiology, Diagnosis and Clinical Aspects of Smith-Lemli-Opitz Syndrome. Expert opinion on orphan drugs. 2015. PMID: 25734025
  2. Waterham HR, Hennekam RC. Mutational spectrum of Smith-Lemli-Opitz syndrome. American journal of medical genetics. Part C, Seminars in medical genetics. 2012. PMID: 23042628
  3. Tulenko TN, Boeze-Battaglia K, Mason RP. A membrane defect in the pathogenesis of the Smith-Lemli-Opitz syndrome. Journal of lipid research. 2006. PMID: 16258167
  4. Correa-Cerro LS, Porter FD. 3beta-hydroxysterol Delta7-reductase and the Smith-Lemli-Opitz syndrome. Molecular genetics and metabolism. 2005. PMID: 15670717
  5. Waye JS, Krakowiak PA, Wassif CA. Identification of nine novel DHCR7 missense mutations in patients with Smith-Lemli-Opitz syndrome (SLOS). Human mutation. 2005. PMID: 15954111
  6. Yu H, Patel SB. Recent insights into the Smith-Lemli-Opitz syndrome. Clinical genetics. 2005. PMID: 16207203
  7. Nowaczyk MJ, Martin-Garcia D, Aquino-Perna A. Founder effect for the T93M DHCR7 mutation in Smith-Lemli-Opitz syndrome. American journal of medical genetics. Part A. 2004. PMID: 14981719
  8. Jira PE, Waterham HR, Wanders RJ. Smith-Lemli-Opitz syndrome and the DHCR7 gene. Annals of human genetics. 2003. PMID: 12914579
  9. Nowaczyk MJ, Waye JS. The Smith-Lemli-Opitz syndrome: a novel metabolic way of understanding developmental biology, embryogenesis, and dysmorphology. Clinical genetics. 2001. PMID: 11453964
  10. Porter FD. RSH/Smith-Lemli-Opitz syndrome: a multiple congenital anomaly/mental retardation syndrome due to an inborn error of cholesterol biosynthesis. Molecular genetics and metabolism. 2000. PMID: 11001807
Educational content. This page is not medical or genetic advice, is not individually reviewed by a clinician for each reader, and should not replace a consultation with a qualified healthcare professional or genetic counsellor. If you are considering genetic testing or acting on a test result, book a consultation.
Data sources Last updated 6 September 2026. Content compiled from HGNC · MedlinePlus Genetics · ClinGen · Genomics England PanelApp · NHS National Genomic Test Directory · ClinVar · UniProt · AlphaFold .