The DHCR7 gene gives your body instructions for the last step of making cholesterol, a substance needed for cell membranes, hormones, and early development. This gene helps your body keep cholesterol levels balanced as cells grow and organs form. If the gene does not work well, cholesterol can be too low and related substances can build up. When a person inherits nonworking copies from both parents, this causes Smith-Lemli-Opitz syndrome, which can affect growth, learning, and physical development.
What is a gene?
A gene is a stretch of DNA that carries instructions your cells use to make molecules or to regulate activities in the body. Some genes provide the directions for building proteins, which are the parts of cells that do much of the work. Others are used mainly to guide when certain processes happen, where they happen, and how active they are. Taken together, genes affect how your body grows and works, and they may also influence how you react to food, stress, or medicines. For a deeper look at this topic, more information is available in the LearnHub.
Overview
DHCR7Gene function
What if the gene works
The DHCR7 gene helps your body make cholesterol by carrying out the last step in the process. This supports cell membranes, hormone production, and brain development.
Risk
What if the gene does not work
Variants in the DHCR7 gene can cause Smith-Lemli-Opitz syndrome, affecting growth, learning, behavior, and body development before and after birth. Effects can range from mild to more severe, depending partly on the variant.
Treatment
What does that mean for your treatment
Pathogenic variants in the DHCR7 gene can make cholesterol supplementation part of treatment, often through diet or formula with added cholesterol. This aims to raise cholesterol levels and may lower buildup of related sterols, which are cholesterol-like substances. Bile acid replacement may be added in selected people with liver or bile acid problems. Simvastatin has been studied in some cases, but it is not standard care.
Conditions associated with DHCR7
Gene function
What if the gene works
Your cells need cholesterol to build sturdy membranes and handle everyday work. A core part of how the DHCR7 gene helps make cholesterol is carrying out the final conversion step inside cells. This keeps a key building material available for many tissues.
The DHCR7 gene directs the last step of cholesterol production in your cells. It turns 7-dehydrocholesterol, an earlier cholesterol form, into cholesterol.
By supplying cholesterol, this gene helps cell membranes stay stable and flexible. That allows cells to keep their shape and manage what moves in and out.
This gene also helps keep the right balance between cholesterol and 7-dehydrocholesterol during cholesterol production. That supports smooth, steady cell activity across many tissues.
What is a variant?
A genetic variant is a small difference in the DNA sequence within a gene. These changes are common and help account for normal human diversity, including differences in appearance, metabolism, or how the body responds to environmental influences. Many variants do not cause any noticeable effect and are simply part of natural genetic variation. In some cases, though, a variant can change how a gene works more substantially and may contribute to or cause a genetic condition.
Genetic variants
What if the gene does not work
Variants in the DHCR7 gene can lower or block the enzyme’s final step in cholesterol production, so a cholesterol precursor called 7-dehydrocholesterol builds up while cholesterol drops. Some changes leave partial activity, but more severe variants can markedly reduce enzyme stability or function. This range helps explain how DHCR7 variants affect cholesterol production and why Smith-Lemli-Opitz syndrome may appear earlier or be more noticeable when very little enzyme activity remains.
How variants are linked to conditions
Pathogenic variants in both copies of the DHCR7 gene cause Smith-Lemli-Opitz syndrome, a genetic condition that can affect growth, development, feeding, and physical features. The DHCR7 gene Smith-Lemli-Opitz syndrome connection is well established in clinical genetics. People with one altered copy are usually carriers and typically do not have the condition.
A variant is not necessarily a diagnosis
Genetic variants are a routine part of human biology and are common across the general population. Most do not have a direct effect on health and simply reflect natural human diversity. For many genes, carrying a variant associated with a condition suggests a possible link rather than a definite diagnosis, especially when several genes and environmental factors are involved. In some situations, though, a single well-characterized variant in a specific gene can be enough to confirm a diagnosis.
Are there things that can increase or change my risk?
For DHCR7, risk is mainly shaped by the variants a baby inherits, especially if both parents carry a harmful change in this gene. The exact variants can affect how severe the condition is, and cholesterol levels during pregnancy may also influence severity, but they do not remove the underlying genetic risk.
Inheritance of DHCR7 variants
DHCR7-related Smith-Lemli-Opitz syndrome follows an autosomal recessive inheritance pattern. This means a child inherits one DHCR7 variant from each parent, and parents who carry one variant are usually unaffected carriers. When both parents are carriers, each pregnancy has a 25% chance of an affected child, a 50% chance of a child who is also a carrier, and a 25% chance of a child who inherits neither variant. In practical terms, the DHCR7 inheritance pattern is the same for sons and daughters.
What does my DHCR7 result mean for my family?
For families with a DHCR7-related condition, close relatives may also carry a changed copy of the gene, even if they do not have symptoms. Brothers and sisters may be affected or may be carriers, and other blood relatives may also be carriers. This can matter for future pregnancies, because relatives who carry a DHCR7 variant can pass it on to their children.
Genetic information
Genetic testing
How you find out about variants
To look for changes in the DHCR7 gene, DHCR7 genetic testing uses a blood or saliva sample. A lab reads the gene’s DNA code to check for variants, often as part of a broader panel or exome test. Results can confirm whether a person carries a disease-causing variant or is a carrier.
When should I consider getting a genetic test?
Genetic testing for the DHCR7 gene may be considered when a baby or child has signs that fit Smith-Lemli-Opitz syndrome, such as slow growth, birth differences, or developmental delay. It can also help if this condition runs in your family or if a pregnancy screening test raises concern.
A genetic result is only one part of your health story
A genetic finding can provide useful insight, but how much it explains varies with the condition and the kind of variant identified. Many factors, including age, lifestyle, environment, and medical history, also shape how the body works over time. For some conditions, especially those influenced by many genes, genetic information offers context rather than certainty and is best understood together with other parts of care. In other situations, a genetic result can give a clear answer. In areas like medication response, it can also help place personal experiences in context.
Pharmacogenetics
How variants shape your response to medicine
Genetic variation can affect how people respond to medicines. Two people taking the same treatment may process it differently, so one may get the expected benefit while another may notice less effect or be more sensitive to side effects. This happens because genes help control how the body absorbs, breaks down, and responds to many drugs. These differences are common and are one reason medication response can vary from person to person.
What is Pharmacogenetics?
Pharmacogenetics examines the ways genetic variation can affect a person’s response to medicines. It studies links between genes and medications to clarify why the same treatment may not work the same way for everyone. With many drugs, genes can influence both how powerfully a medicine works and how the body handles it. This information can support treatment choices that are more informed and more tailored to the individual. More detail on this subject is available in the LearnHub.
Drugs influenced by the DHCR7 gene
When should I seek medical advice?
There is not yet a broadly confirmed role for this gene in predicting how medicines will work, so questions about side effects, new symptoms, or the best treatment for you are best discussed with your doctor.
History
Doctors had long recognized a pattern of birth differences, growth concerns, and learning challenges in some children, but the cause remained unclear for many years. In the 1960s, this pattern was formally described as Smith-Lemli-Opitz syndrome. Decades later, researchers linked the condition to changes in the DHCR7 gene, connecting earlier clinical observations to a specific inherited cause. From these first observations, research expanded steadily. This discovery was an important step because it tied a recognizable syndrome to a cholesterol-making pathway and improved genetic diagnosis for affected families. Over time, the history of the DHCR7 gene became part of a broader shift in medicine, from describing conditions by appearance alone to understanding their genetic basis.