The ALG5 gene helps cells build a sugar tag that is attached to many proteins so they can fold and work properly. If the gene does not work well, proteins may be made incorrectly, which can affect the brain, muscles, liver, and growth. A small number of people with pathogenic variants in the ALG5 gene have a rare congenital disorder of glycosylation, often linked with developmental delay, low muscle tone, seizures, and feeding problems. This gene is mainly known in rare disease medicine rather than in popular culture.
What is a gene?
Within your DNA, a gene is a stretch that holds instructions your cells use to make molecules or regulate processes in the body. Some genes carry the directions for producing proteins, the parts of cells that do the work. Others mainly guide when certain processes happen, where they happen, and how strongly they are carried out. As a group, genes affect how the body grows and works, and they can influence how you respond to food, stress, or medicines. To explore this topic in more detail, you can find more in the LearnHub.
Overview
ALG5Gene function
What if the gene works
The ALG5 gene helps cells attach a glucose sugar while proteins are being made. This supports proper protein folding and helps many proteins work normally throughout the body.
Risk
What if the gene does not work
Variants in the ALG5 gene can cause a congenital disorder of glycosylation with delayed development, low muscle tone, seizures, and eye problems; milder and more severe variants may affect when symptoms begin and how strongly they appear.
Treatment
What does that mean for your treatment
For pathogenic variants in the ALG5 gene, no ALG5-specific treatment or drug selection approach is currently established.
Conditions associated with ALG5
Gene function
What if the gene works
Your cells constantly make proteins that need small sugar chains to fold and travel correctly. Inside the endoplasmic reticulum, a part of the cell that processes proteins, the ALG5 gene supports an early step in that setup. Its work helps prepare many proteins for their usual jobs throughout the body.
The ALG5 gene helps your cells make dolichol phosphate glucose, a sugar carrying molecule in the endoplasmic reticulum (the cell's protein processing area). This molecule provides glucose for an early protein building step.
Through this step, ALG5 supports how the body adds sugar chains to proteins in the endoplasmic reticulum. These chains help many proteins fold into a stable shape before they move to where they are needed.
When sugar chains are built correctly, cells can check new proteins more smoothly and keep them on track. This supports steady protein function across many tissues.
What is a variant?
A genetic variant is a small alteration in the DNA sequence of a gene. These changes are common and are part of normal human diversity, including differences in appearance, metabolism, and how the body responds to environmental influences. Many variants do not have any noticeable effect and simply represent natural genetic variation. In some cases, though, a variant can change a gene’s function more substantially and may contribute to, or cause, a genetic condition.
Genetic variants
What if the gene does not work
Variants in the ALG5 gene affect glycosylation by reducing or blocking the enzyme’s ability to make a molecule that carries sugar for cells to add sugar chains to proteins. Some changes mainly make the protein unstable, while others alter its working site and sharply lower activity. Milder variants may leave some function, but more severe variants can cause near complete loss of function. In ALG5-CDG, this range often relates to when features begin and how broad they are.
How variants are linked to conditions
Pathogenic variants in the ALG5 gene cause ALG5-CDG, a rare inherited congenital disorder of glycosylation. People with this condition may have developmental delay, low muscle tone, seizures, feeding difficulties, and eye or liver findings, though the pattern can vary from person to person. In medical genetics, finding pathogenic variants in both copies of the ALG5 gene can confirm the diagnosis of ALG5 congenital disorder of glycosylation.
A variant is not necessarily a diagnosis
Gene variants are a normal part of human biology and are widespread in the general population. Most do not directly affect health and instead represent 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 is enough to confirm a diagnosis.
Are there things that can increase or change my risk?
For ALG5, risk is mainly shaped by genetics rather than lifestyle. A child is at risk of this condition when they inherit a disease-causing ALG5 change from both parents, so family history, known carrier status, and parents being biologically related can raise the chance. There is not enough evidence to say that diet, exercise, or other everyday factors change this risk.
Inheritance of ALG5 variants
ALG5-related conditions are inherited in an autosomal recessive pattern. This means a person inherits one nonworking copy of the ALG5 gene from each parent. Parents who each carry one ALG5 gene variant usually do not have the condition themselves, but with each pregnancy they have a 25% chance of having an affected child, a 50% chance of having a child who is a carrier, and a 25% chance of having a child with two working copies. In families asking how variants of the ALG5 gene are inherited, sons and daughters are affected at the same rate.
What does my ALG5 result mean for my family?
For families with an ALG5-related condition, the pattern is usually recessive, which means parents are often healthy carriers. Brothers and sisters may also be carriers, and in some families a sibling could also be affected. Close relatives may want to learn whether the same gene change runs in the family, especially when planning children.
Genetic information
Genetic testing
How you find out about variants
To find out about ALG5 variants, doctors use genetic testing on a blood sample or saliva sample. ALG5 genetic testing usually reads the DNA sequence of the ALG5 gene, and some tests also check for missing or extra pieces of DNA. Results may identify a disease-causing variant, no relevant variant, or a finding that is still unclear.
When should I consider getting a genetic test?
Consider testing for the ALG5 gene if a child has signs of a rare inherited condition such as developmental delay, low muscle tone, seizures, or feeding problems, especially when doctors suspect a condition affecting how the body processes sugars. Testing can also help when there is a known ALG5 change in the family or a previous affected child.
A genetic result is only one part of your health story
Genetic results can be informative, but what they can tell you varies based on the condition and the kind of variant involved. Lifestyle, environment, age, and medical history are among the many factors that influence how the body functions over time. For some conditions, especially those shaped by many genes, genetic information provides context rather than certainty and is best understood together with other parts of care. In other situations, a genetic result may give a clear answer. In areas like medication response, these results can also help put individual experiences into context.
Pharmacogenetics
How variants shape your response to medicine
Genetic variation can affect how people respond to medicines. Small differences in genes can change how the body breaks down a drug, moves it through the body, or responds to it at its target. This helps explain why the same medication may work well for one person, work less well for another, or cause more side effects in someone who is more sensitive to it.
What is Pharmacogenetics?
Pharmacogenetics explores how genetic differences shape the way a person responds to medication. By examining links between genes and drugs, it helps explain why the same treatment may work differently from one person to another. For many medications, genes influence how strongly a drug works or how the body handles it. This information can support treatment decisions that are better informed and more individualized. More on this topic is available in the LearnHub.
Drugs influenced by the ALG5 gene
When should I seek medical advice?
There is not currently a broadly confirmed role for this gene in guiding how medicines are chosen or used. If you have new symptoms, troublesome side effects, or questions about any treatment, it is a good idea to speak with your doctor or pharmacist.