Your body relies on this gene to help turn cholesterol into bile acids, which support digestion and help keep cholesterol byproducts from building up. If the CYP27A1 gene does not work properly, it can cause cerebrotendinous xanthomatosis, a condition that may lead to chronic diarrhea, early cataracts, tendon lumps, and later problems with balance, movement, or thinking. This condition is inherited when both copies of the gene carry a pathogenic variant.
What is a gene?
Genes are segments of DNA that carry instructions cells use to make molecules or regulate activities in the body. Some genes hold the information needed to produce proteins, the parts of cells that do the work. Others mainly guide when certain processes happen, where they occur, and how strongly they run. Together, genes affect how the body develops and works, and they can influence how you respond to food, stress, or medications. You can find more on this topic in the LearnHub.
Overview
CYP27A1Gene function
What if the gene works
The CYP27A1 gene helps your body convert cholesterol into bile acids, which support fat digestion and cholesterol balance. Its protein also contributes to vitamin D processing.
Risk
What if the gene does not work
When the CYP27A1 gene does not work properly, people can develop cerebrotendinous xanthomatosis, with fat buildup that may cause cataracts, tendon lumps, diarrhea, and nerve symptoms. Milder or more severe variants can affect when symptoms begin and how they appear.
Treatment
What does that mean for your treatment
A pathogenic or loss-of-function variant in the CYP27A1 gene usually points to treatment with chenodeoxycholic acid. This bile acid replacement lowers cholestanol buildup and is the main treatment linked to CYP27A1. Starting it early can improve lab markers and may help stabilize or lessen symptoms. A statin is sometimes added if cholestanol stays high.
Conditions associated with CYP27A1
Gene function
What if the gene works
Your body uses the CYP27A1 gene to help manage cholesterol every day. Its protein takes part in making bile acids, which help digest fats and give the body a way to clear cholesterol. This is a key part of how the liver and other tissues keep cholesterol handling steady.
The CYP27A1 gene helps start and continue the conversion of cholesterol into bile acids. These bile acids help with fat digestion and provide an important route for cholesterol removal.
Inside cells, this gene adds oxygen to cholesterol-related molecules so they can be changed step by step. That makes these fats easier for the body to process in an orderly way.
By helping form bile acid building blocks, the CYP27A1 gene supports normal cholesterol balance in the liver and other tissues. Some of the products it makes can also move out of cells more easily than cholesterol itself.
What is a variant?
A genetic variant is a small difference in the DNA sequence of a gene. These changes are common and help account for normal human diversity, such as differences in appearance, metabolism, or how the body responds to environmental influences. Many variants do not have any noticeable effect and simply represent natural genetic variation. In some situations, however, a variant can change how a gene functions more substantially and may contribute to or cause a genetic condition.
Genetic variants
What if the gene does not work
Many variants in the CYP27A1 gene affect bile acid production by changing the enzyme’s shape, stability, or amount, which can leave it partly active or nearly inactive. Milder variants may preserve some activity, while more disruptive variants, including truncating changes that shorten the protein, often greatly reduce or abolish function. In cerebrotendinous xanthomatosis, this functional range can influence how early features appear and how broad they are.
How variants are linked to conditions
Disease-causing variants in both copies of the CYP27A1 gene cause cerebrotendinous xanthomatosis, also called CTX. This well-established link between CYP27A1 gene variants and cerebrotendinous xanthomatosis can include early cataracts, long-term diarrhea, tendon lumps called xanthomas, and changes in walking, balance, or thinking over time. People with one altered copy are usually carriers rather than affected.
A variant is not necessarily a diagnosis
Genetic variants are a usual part of human biology and are widespread in the general population. Most do not directly affect health and instead reflect normal human variation. For many genes, having 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 understood variant in a specific gene is enough to confirm a diagnosis.
Are there things that can increase or change my risk?
For CYP27A1, risk is mainly shaped by inheritance: it rises if both parents carry a nonworking copy of the gene, especially in families with cerebrotendinous xanthomatosis. There is not enough evidence to say lifestyle changes lower the chance of having this genetic condition, but early diagnosis and treatment can greatly reduce complications.
Inheritance of CYP27A1 variants
Variants in the CYP27A1 gene are inherited in an autosomal recessive pattern. This means a person usually needs to inherit two disease-causing variants, one from each parent, to have CYP27A1-related cerebrotendinous xanthomatosis. Parents who each carry one variant are typically unaffected carriers, and with each pregnancy they have a 25% chance of having an affected child, a 50% chance of having a carrier child, and a 25% chance of having a child without the familial variants. Because the CYP27A1 gene is on chromosome 2, this inheritance pattern affects males and females equally.
What does my CYP27A1 result mean for my family?
For families with a CYP27A1 change linked to disease, the pattern is usually recessive, which means close relatives may also carry the same change even if they feel well. Brothers and sisters could be affected or be carriers, and parents are often carriers. Other relatives, such as adult children or cousins, may also want to learn whether the variant runs in the family.
Genetic information
Genetic testing
How you find out about variants
CYP27A1 genetic testing for cerebrotendinous xanthomatosis looks for variants in a DNA sample, usually from blood or saliva. A lab reads the CYP27A1 gene to check for changes linked to this condition and can show whether a person carries one or two variants. Results may identify a disease-causing variant, a harmless change, or a variant of uncertain significance.
When should I consider getting a genetic test?
Consider CYP27A1 testing if you or your child has signs of a rare inherited condition called cerebrotendinous xanthomatosis, which can cause long-lasting diarrhea, early cataracts, lumps on tendons, or later nerve and movement problems. It can also help when a close relative has this condition or a known CYP27A1 variant.
A genetic result is only one part of your health story
A genetic finding can provide meaningful insight, but how much it explains depends on the condition and on the type of variant involved. Factors such as lifestyle, environment, age, 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 most useful when considered alongside other parts of care. In other situations, a genetic result can provide a clear answer. In areas like medication response, genetic results can also help place individual experiences in context.
Pharmacogenetics
How variants shape your response to medicine
Genetic variation can affect how people respond to medicines. Small differences in the genes that help the body absorb, break down, transport, or respond to a drug can mean that the same treatment works differently from one person to another. This is common and can influence how much benefit someone gets or how sensitive they are to side effects.
What is Pharmacogenetics?
Pharmacogenetics examines how genetic differences can influence a person’s response to medications. It looks at connections between genes and drugs to help explain why the same treatment can work differently from one person to another. For many medicines, genes help shape how strongly a drug works or how the body processes it. This information can support treatment decisions that are more informed and more individualized. More detailed information on this topic is available in the LearnHub.
Drugs influenced by the CYP27A1 gene
When should I seek medical advice?
There is not yet a broadly confirmed role for this gene in predicting how people respond to medicines. If you have concerns about side effects, a new prescription, or how your medicines fit with your overall health, talk with your doctor or pharmacist.
History
Throughout history, people described families with tendon lumps, cataracts, and neurologic symptoms that were later recognized as cerebrotendinous xanthomatosis. Initially understood only through visible traits, later recognized as tied to a specific gene, this condition drew closer study in the late 20th century. In the 1990s, researchers linked cerebrotendinous xanthomatosis to variants in the CYP27A1 gene, connecting a long-observed inherited pattern to a specific genetic cause. From these first observations, research expanded steadily. That discovery helped explain why affected families could show a similar mix of symptoms across generations. It also opened the way for clearer diagnosis and earlier recognition in people whose symptoms had once seemed unrelated.