The RAB33B gene helps cells move and sort proteins, especially in the cell’s packing and shipping system. If it does not work properly, bones and cartilage may not develop in the usual way, which can lead to a skeletal condition with short stature, changes in the spine and joints, and early wear of the hips. People with two disease-causing variants in the RAB33B gene can develop Smith-McCort dysplasia, while carriers usually remain well.
What is a gene?
A gene is a stretch of DNA that holds information cells use to make molecules or manage processes in the body. Some genes provide the instructions for producing proteins, the parts of cells that do much of the work. Others mainly control when certain processes happen, where they take place, and how active they are. Taken together, genes affect how the body develops and works, and they can also shape how you respond to food, stress, or medications. To explore this topic in more detail, you can learn more in the LearnHub.
Overview
RAB33BGene function
What if the gene works
The RAB33B gene helps cells move proteins through the Golgi apparatus, a packaging and shipping center inside the cell. It also supports autophagy, the process cells use to recycle worn out parts.
Risk
What if the gene does not work
Faults in the RAB33B gene can cause Smith-McCort skeletal dysplasia, with short stature, bone and spine changes, and hip problems. Milder and more severe variants can affect which features appear and how marked they are.
Treatment
What does that mean for your treatment
For a pathogenic or loss-of-function variant in the RAB33B gene, no RAB33B-specific treatment or management approach is currently established. The RAB33B gene is being studied in basic research on cell transport and bone development, but this has not led to guideline-based drug choices.
Conditions associated with RAB33B
Gene function
What if the gene works
Inside your cells, the RAB33B gene helps the cell’s shipping system run smoothly. A key part of RAB33B gene function is guiding traffic around the Golgi apparatus, the cell’s packaging center. This supports the routine handling of proteins and fats so they reach the right place at the right time.
The RAB33B gene helps move tiny cargo packets between parts of the Golgi apparatus. This lets proteins and fats be processed, sorted, and sent onward in an orderly way.
Some cell materials need to travel back from the Golgi apparatus to the endoplasmic reticulum, where many proteins are first made. RAB33B helps guide this return trip so the shipping network stays balanced.
The RAB33B gene supports the usual stacked shape of the Golgi apparatus. When this packaging center stays organized, cells can manage routine delivery jobs more smoothly.
What is a variant?
A genetic variant is a small difference in the DNA sequence within a gene. These differences are common and are part of normal human diversity, including differences in appearance, metabolism, or how the body responds to environmental influences. Many variants have no noticeable effect and simply represent 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 RAB33B gene can affect protein function by changing its shape, shortening it, or making it less stable. These changes may weaken its ability to bind and use GTP, a small energy-carrying molecule, or to interact with other cell proteins, which can disrupt Golgi trafficking, the cell’s shipping system. Milder variants may leave some activity, while more severe variants can cause near-complete loss of function and are often linked to earlier or more marked features of Smith-McCort dysplasia.
How variants are linked to conditions
Pathogenic variants in the RAB33B gene cause Smith-McCort dysplasia, a rare inherited skeletal condition. When a person has two disease causing variants, RAB33B gene variants linked to Smith-McCort dysplasia can lead to short stature, spine and hip changes, and other differences in bone growth that often become clearer in childhood. This is a confirmed genetic diagnosis rather than a common risk finding.
A variant is not necessarily a diagnosis
Gene variants are a normal feature of human biology and are common throughout the general population. Most have no direct impact on health and simply represent natural human diversity. For many genes, carrying a variant associated with a condition indicates a possible link rather than a definitive diagnosis, especially when several genes and environmental factors contribute. In some situations, though, a single well-characterized variant in a particular gene can be enough to confirm a diagnosis.
Are there things that can increase or change my risk?
For RAB33B, risk is mainly set by inheritance: it is higher when both parents carry a changed copy of the RAB33B gene, and it can also be higher in families where the parents are related by blood. There is not enough evidence to say that diet, exercise, or other lifestyle factors lower this inherited risk.
Inheritance of RAB33B variants
Variants in the RAB33B gene linked to RAB33B-related skeletal conditions are inherited in an autosomal recessive pattern. This means a child usually inherits one altered copy from each parent, and both parents are often healthy carriers. When both parents carry a RAB33B gene variant, each pregnancy has a 25% chance of the child inheriting both altered copies, which explains how RAB33B variants are inherited in families. Sons and daughters are affected at the same rate.
What does my RAB33B result mean for my family?
Changes in the RAB33B gene are linked to a rare bone growth condition that usually runs in families in a recessive pattern. For family members, this often means parents may be healthy carriers, and brothers or sisters could also be affected or be carriers even if they seem well. Other relatives may also carry the gene change, especially on the same side of the family.
Genetic information
Genetic testing
How you find out about variants
To find out whether you carry a variant in the RAB33B gene, a lab can analyze DNA from a blood sample, saliva, or a cheek swab. This kind of RAB33B genetic testing reads the gene's code and compares it with the usual sequence to identify variants that may help explain a confirmed or suspected genetic condition.
When should I consider getting a genetic test?
Genetic testing for the RAB33B gene may be considered when a child has signs of a bone growth condition such as short stature, spine changes, and joint or chest shape differences, especially if similar features run in the family. It can also help confirm the cause when doctors suspect Smith-McCort dysplasia.
A genetic result is only one part of your health story
Genetic findings can be informative, but how much they reveal varies based on the condition and the kind of variant involved. Many factors, including lifestyle, environment, age, and medical history, influence how the body functions over time. For some conditions, especially those shaped by many genes, genetic information offers context rather than certainty and is most useful when viewed alongside other parts of care. In other situations, a genetic result can provide a clear answer. In areas such as medication response, it can also help explain individual experiences.
Pharmacogenetics
How variants shape your response to medicine
Genetic variation can affect how people respond to medicines. This can change how the body breaks down a drug, moves it through the body, or reacts to it at its target. As a result, the same medication may work better for some people, seem less effective for others, or cause more side effects in some than in others.
What is Pharmacogenetics?
Pharmacogenetics examines how genetic differences can shape a person’s response to medications. It focuses on gene drug relationships to help explain why the same treatment may work differently from one person to another. For many medicines, genes influence both how strongly a drug works and how the body processes it. This information can support more informed, individualized treatment decisions. More about this topic is available in the LearnHub.
Drugs influenced by the RAB33B 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 treatment choices are best discussed with your doctor.
History
RAB33B entered the medical literature during efforts to catalog the large RAB family of genes. Its medical importance became clearer in the 2010s, when researchers linked changes in the RAB33B gene to Smith-McCort dysplasia, a rare inherited condition affecting bone growth. This discovery helped distinguish that condition from similar skeletal conditions that can look alike early in life. From these first observations, research expanded steadily, and reports from additional families helped confirm the connection. Over time, descriptions became more precise, and the RAB33B gene came to be recognized as part of the genetics of rare skeletal conditions.