Skip to content

We are currently in beta

Please enjoy the existing content while we continue to fix and enhance your experience.

We would love to receive any feedback or comments that you'd like to share.

You can contact us here

Journeys of Life

My Library
About StoryMD
Newsletter
Help Center
Contact Us

Privacy Policy
Terms of Service
Accessibility

Find us on facebook
Find us on instagram
Find us on linkedin
Find us on pinterest
Find us on twitter
Find us on youtube

© 2024 StoryMD Inc. All rights reserved.

X-Linked Creatine Deficiency

Table of Contents

X-Linked Creatine Deficiency

SLC6A8 Deficiency; SLC6A8-Related Creatine Transporter Deficiency; X-linked Creatine Transporter Deficiency

Creatine is needed for the body to store and use energy properly. X-linked creatine deficiency is an inherited disorder that impairs the body's ability to bring creatine into cells. This primarily affects the brain leading to intellectual disability, ranging from mild to severe, and delayed speech development. Explore causes, symptoms, and treatment.

Medical visualization of a human X chromosome

Image by TheVisualMD

About

Human Brain

Image by lifesciencedb. Original uploader was BrianMSweis at en.wikipedia

Human Brain

Human brain (hypothalamus=red, amygdala=green, hippocampus/fornix=blue, pons=gold, pituitary gland=pink)

Image by lifesciencedb. Original uploader was BrianMSweis at en.wikipedia

What Is X-Linked Creatine Deficiency?

X-linked creatine deficiency is an inherited disorder that primarily affects the brain. People with this disorder have intellectual disability, which can range from mild to severe, and delayed speech development. Some affected individuals develop behavioral disorders such as attention-deficit/hyperactivity disorder (ADHD) or autistic behaviors that affect communication and social interaction. They may also experience seizures. Children with X-linked creatine deficiency may grow slower and develop motor skills, such as sitting and walking, later than their peers. Affected individuals tend to tire easily.

A small number of people with X-linked creatine deficiency have additional signs and symptoms including abnormal heart rhythms, an unusually small head (microcephaly), or distinctive facial features such as a broad forehead and a flat or sunken appearance of the middle of the face (midface hypoplasia).

Source: MedlinePlus Genetics

Causes

Genomic variant

Image by National Human Genome Research Institute

Genomic variant

There are roughly 4 to 5 million such genomic variants in an individual’s genome. These variants may be unique to that individual or occur in others as well.

Image by National Human Genome Research Institute

What Causes X-Linked Creatine Deficiency?

Variants (also known as mutations) in the SLC6A8 gene cause X-linked creatine deficiency. The SLC6A8 gene provides instructions for making a protein that transports a compound called creatine into cells. Creatine is needed for the body to store and use energy properly.

SLC6A8 gene variants impair the transporter protein's ability to bring creatine into cells, resulting in a shortage (deficiency) of creatine. The effects of creatine deficiency are most severe in organs and tissues that require large amounts of energy, especially the brain.

Source: MedlinePlus Genetics

SLC6A8 Gene

Ideogram of human chromosome X

Image by Office of Biological and Environmental Research of the U.S. Department of Energy Office of Science, the Biological and Environmental Research Information System, Oak Ridge National Laboratory.

Ideogram of human chromosome X

Selected genes, traits, and disorders associated with the chromosome listed; (blue and violet) regions reflecting the unique patterns of light and dark bands seen on human chromosomes stained to allow viewing through a light microscope; (red) the centromere, or constricted portion, of each chromosome; (yellow) chromosomal regions that vary in staining intensity and sometimes are called hererochromatin (meaning “different color”); (lines between yellow) variable regions, called stalks, that connect a very small chromosome arm (a “satellite”) to the chromosome.

Image by Office of Biological and Environmental Research of the U.S. Department of Energy Office of Science, the Biological and Environmental Research Information System, Oak Ridge National Laboratory.

SLC6A8 Gene: Solute Carrier Family 6 Member 8

Normal Function

The SLC6A8 gene provides instructions for making a protein called sodium- and chloride-dependent creatine transporter 1. This protein transports the compound creatine into cells. Creatine is needed for the body to store and use energy properly.

Health Conditions Related to Genetic Changes

X-linked creatine deficiency

At least 80 mutations in the SLC6A8 gene have been identified in people with X-linked creatine deficiency, a disorder that causes intellectual disability, behavioral problems, seizures, and muscle weakness. SLC6A8 gene mutations impair the ability of the transporter protein to bring creatine into cells, resulting in a creatine shortage (deficiency). The effects of creatine deficiency are most severe in organs and tissues that require large amounts of energy, especially the brain.

Other Names for This Gene

creatine transporter 1
creatine transporter SLC6A8
CRT
CRTR
CT1
MGC87396
SC6A8_HUMAN
sodium- and chloride-dependent creatine transporter 1
solute carrier family 6 (neurotransmitter transporter), member 8
solute carrier family 6 (neurotransmitter transporter, creatine), member 8

Genomic Location

The SLC6A8 gene is found on the X chromosome.

Source: MedlinePlus Genetics

Inheritance

X-Linked Patterns of Inheritance

Image by CNX Openstax

X-Linked Patterns of Inheritance

A chart of X-linked dominant inheritance patterns differs depending on whether (a) the father or (b) the mother is affected with the disease. (credit: U.S. National Library of Medicine)

Image by CNX Openstax

How Is X-Linked Creatine Deficiency Inherited?

This condition is inherited in an X-linked pattern. The gene associated with this condition is located on the X chromosome, which is one of the two sex chromosomes. In females (who have two X chromosomes), a variant in one of the two copies of the gene in each cell may or may not cause the disorder. In males (who have only one X chromosome), a variant in the only copy of the gene in each cell causes the disorder. A characteristic of X-linked inheritance is that fathers cannot pass X-linked traits to their sons.

In most cases of X-linked inheritance, males experience more severe symptoms of the disorder than females. About half of females with one altered copy of the SLC6A8 gene in each cell have intellectual disability, learning difficulties, or behavioral problems. Other females with one altered copy of the SLC6A8 gene in each cell have no noticeable neurological problems.

Source: MedlinePlus Genetics

Additional Materials (1)

X-Linked

X-linked, as related to genetics, refers to characteristics or traits that are influenced by genes on the X chromosome. Humans and most other mammals have two sex chromosomes, X and Y. Females have two X chromosomes in their cells, while males have one X and one Y. In the case of an X-linked disease, it is usually males that are affected because they have a single copy of the X chromosome that carries the disease-causing mutation. In females, the presence of a second, non-mutated copy may cause different, milder, or no symptoms of a sex-linked disorder.

Image by National Human Genome Research Institute (NHGRI)

X-Linked

National Human Genome Research Institute (NHGRI)

Symptoms

Brain's electrical reaction - seizures

Image by TheDigitalArtist/Pixabay

Brain's electrical reaction - seizures

Image by TheDigitalArtist/Pixabay

What Are the Signs and Symptoms of X-Linked Creatine Deficiency?

Signs and symptoms may include:

Intellectual disability
Delayed speech and language development
Behavioral issues
Seizures
Low muscle tone (hypotonia)
Uncoordinated movement (ataxia)
Gastrointestinal symptoms

Symptoms usually begin in childhood, but sometimes occur much later. Some of the symptoms of X-linked creatine deficiency may get worse over time, especially intellectual disability.

Source: Genetic and Rare Diseases (GARD) Information Center

Diagnosis

Genetic testing

Image by genome.gov

Genetic testing

Genetic testing fact sheet

Image by genome.gov

How Is X-Linked Creatine Deficiency Diagnosed?

X-linked creatine deficiency is diagnosed based on the symptoms, clinical exam, and the results of genetic testing.

Screening tests looking for levels of specific chemicals in the urine are often used prior to genetic testing.

Source: Genetic and Rare Diseases (GARD) Information Center

Genetic Testing

Genetic Testing

Also called: DNA Testing, Mutation Screening, Genetic Test

Genetic testing is a type of test that analyze your cells or tissue to look for any changes in your DNA. Genetic tests may be used to identify increased risks of health problems, to choose treatments, or to assess responses to treatments.

Genetic Testing

Also called: DNA Testing, Mutation Screening, Genetic Test

Genetic testing is a type of test that analyze your cells or tissue to look for any changes in your DNA. Genetic tests may be used to identify increased risks of health problems, to choose treatments, or to assess responses to treatments.

{"label":"Genetic test reference range","description":"This is a type of test that analyzes cells or tissue to look for changes in a particular gene, chromosome, or protein of interest. Genetic tests may be used to identify increased risks of health problems, to choose treatments, or to assess responses to treatments. Results are reported as positive, negative or uncertain, and may include specific findings.","scale":"lin","step":0.25,"items":[{"flag":"negative","label":{"short":"Negative","long":"Negative","orientation":"horizontal"},"values":{"min":0,"max":1},"text":"A negative (normal) result means that the test did not find a change that is known to affect health or development in the gene, chromosome, or protein under consideration. This result can indicate that a person is not affected by a particular disorder, is not a carrier of a specific genetic variant, or does not have an increased risk of developing a certain disease. It is possible, however, that the test missed a disease-causing genetic alteration because many tests cannot detect all genetic changes that can cause a particular disorder.","conditions":[]},{"flag":"borderline","label":{"short":"Uncertain","long":"Uncertain","orientation":"horizontal"},"values":{"min":1,"max":2},"text":"An uncertain (variant of unknown or uncertain significance) result means there isn\u2019t enough information about that genetic change to determine whether it is benign (normal) or pathogenic (disease causing). This type of result may be also called uninformative, indeterminate, inconclusive, or ambiguous.","conditions":[]},{"flag":"positive","label":{"short":"Positive","long":"Positive","orientation":"horizontal"},"values":{"min":2,"max":3},"text":"A positive (abnormal) result means that the test found a change in a particular gene, chromosome, or protein of interest. Depending on the purpose of the test, this result may confirm a diagnosis, indicate that a person is a carrier of a particular genetic variant, identify an increased risk of developing a disease (such as cancer), or suggest a need for further testing.","conditions":[]}],"hideunits":true,"value":0.5}[{"negative":0},{"borderline":0},{"positive":0}]
Use the slider below to see how your results affect your health.
Your result is Negative.
A negative (normal) result means that the test did not find a change that is known to affect health or development in the gene, chromosome, or protein under consideration. This result can indicate that a person is not affected by a particular disorder, is not a carrier of a specific genetic variant, or does not have an increased risk of developing a certain disease. It is possible, however, that the test missed a disease-causing genetic alteration because many tests cannot detect all genetic changes that can cause a particular disorder.
Related conditions
Genetic testing may be done for many different reasons, including to:
- Find genetic diseases in unborn babies. This is one type of prenatal testing.
- Screen newborn babies for certain treatable conditions
- Lower the risk of genetic diseases in embryos that were created using assisted reproductive technology
- Find out if you carry a gene for a certain disease that could be passed on to your children. This is called carrier testing.
- See whether you are at increased risk of developing a specific disease. This may be done for a disease that runs in your family.
- Diagnose certain diseases
- Identify genetic changes that may be causing or contributing to a disease that you were already diagnosed with
- Figure out how severe a disease is
- Help guide your doctor in deciding the best medicine and dosage for you. This is called pharmacogenomic testing.
There are no known risks to having a saliva test. There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.
The physical risks of the different types of genetic testing are small. But there can be emotional, social, or financial drawbacks:
- Depending on the results, you may feel angry, depressed, anxious, or guilty. This can be especially true if you are diagnosed with a disease that does not have effective treatments.
- You may be worried about genetic discrimination in employment or insurance
- Genetic testing may give you limited information about a genetic disease. For example, it cannot tell you whether you will have symptoms, how severe a disease might be, or whether a disease will get worse over time.
- Some genetic tests are expensive, and health insurance might only cover part of the cost. Or they may not cover it at all.
- Positive – the test found a genetic change known to cause disease.
- Negative – the test did not find a genetic change known to cause disease. Sometimes a negative result occurs when the wrong test was ordered or there isn’t a genetic cause for that person’s symptoms. A “true negative” is when there is a known genetic change in the family and the person tested did not inherit it. If your test results are negative and there is no known genetic change in your family, a negative test result may not give you a definite answer. This is because you might not have been tested for the genetic change that runs in your family.
- Uncertain – a variant of unknown or uncertain significance means there isn’t enough information about that genetic change to determine whether it is benign (normal) or pathogenic (disease causing).
1. Genetic Testing | CDC. Sep 23, 2022 [accessed on Feb 23, 2022]
2. Genetic Testing: MedlinePlus. National Library of Medicine. Jun 11, 2021 [accessed on Feb 23, 2022]
3. What is genetic testing?: MedlinePlus Genetics [accessed on Feb 23, 2022]
4. Genetic Testing FAQ. Genome.gov [accessed on Feb 23, 2022]
5. Genetic testing and your cancer risk: MedlinePlus Medical Encyclopedia [accessed on Feb 23, 2022]

Normal reference ranges can vary depending on the laboratory and the method used for testing. You must use the range supplied by the laboratory that performed your test to evaluate whether your results are "within normal limits."

Additional Materials (21)

Genetic testing

Genetic testing fact sheet

Image by genome.gov

Genetic testing

Genetic testing existed before the Human Genome Project and the list of diseases that we can already screen for may be longer than you think.

Image by TheVisualMD

Genes and Genetic Defects

Genetic testing isn't new. In the 1960s, doctors were able to test newborn babies for certain rare single-gene disorders, such as phenylketonuria (PKU), a rare metabolic disease that causes mental retardation. (PKU can be prevented with a special diet if it's detected early, which was why it was critical to test newborns.)

Image by TheVisualMD

Mapping Your Future: Screening for Disease Risk

Image by TheVisualMD

Each person with Down syndrome has different talents and the ability to thrive.

Down syndrome is a lifelong condition. Services early in life will often help babies and children with Down syndrome to improve their physical and intellectual abilities. Most of these services focus on helping children with Down syndrome develop to their full potential. These services include speech, occupational, and physical therapy, and they are typically offered through early intervention programs in each state. Children with Down syndrome may also need extra help or attention in school, although many children are included in regular classes.

Image by CDC

genetic analysis

Biotechnology - DNA analysis and treatment

Image by OpenClipart-Vectors/Pixabay

Family history (medicine)

An extended family in Spain

Image by Ojedamd

Biotechnology

This diagram shows the basic method used for extraction of DNA.

Image by CNX Openstax

Genetic Counselor at Sanford Health Explains the Benefits to Genetic Testing

Video by Sanford Health/YouTube

What Is A Genetic Counselor & The Importance of Genetic Counselling | Ambry Genetics

Video by Ambry Genetics/YouTube

How Does The Genetic Testing Process Work? Genetic Testing FAQ | Ambry Genetics

Video by Ambry Genetics/YouTube

Should You Get Genetic Testing During Your Pregnancy?

Video by St. Louis Children's Hospital/YouTube

Debating Embryonic Genetic Testing -- The Doctors

Video by The Doctors/YouTube

Genetic Testing for Cancer — AMITA Health | NBC Chicago Ask the Doc

Video by AMITA Health/YouTube

MedGenome BRCA - Breast Cancer Genetic Testing

Video by MedGenome/YouTube

Genetic Testing for Hereditary Forms of Kidney Cancer - Brian Shuch, MD

Video by UCLA Health/YouTube

Do I need Genetic Testing for Ichthyosis?

Video by foundation for ichthyosis/YouTube

What Is Genetic Testing? Understanding the Process and Its Results

Video by uvahealth/YouTube

How to Understand Your Genetic Testing Results

Video by Breast Cancer Answers®/YouTube

Genetic Testing 101 for People with Rare Diseases

Video by National Organization for Rare Disorders (NORD)/YouTube

What's the difference between genetic and genomic testing?

Video by Cancer Treatment Centers of America - CTCA/YouTube

Genetic testing

genome.gov

Genetic testing

TheVisualMD

Genes and Genetic Defects

TheVisualMD

Mapping Your Future: Screening for Disease Risk

TheVisualMD

Each person with Down syndrome has different talents and the ability to thrive.

CDC

genetic analysis

OpenClipart-Vectors/Pixabay

Family history (medicine)

Ojedamd

Biotechnology

CNX Openstax

1:57

Genetic Counselor at Sanford Health Explains the Benefits to Genetic Testing

Sanford Health/YouTube

1:06

What Is A Genetic Counselor & The Importance of Genetic Counselling | Ambry Genetics

Ambry Genetics/YouTube

0:45

How Does The Genetic Testing Process Work? Genetic Testing FAQ | Ambry Genetics

Ambry Genetics/YouTube

3:04

Should You Get Genetic Testing During Your Pregnancy?

St. Louis Children's Hospital/YouTube

4:40

Debating Embryonic Genetic Testing -- The Doctors

The Doctors/YouTube

1:31

Genetic Testing for Cancer — AMITA Health | NBC Chicago Ask the Doc

AMITA Health/YouTube

2:10

MedGenome BRCA - Breast Cancer Genetic Testing

MedGenome/YouTube

1:37

Genetic Testing for Hereditary Forms of Kidney Cancer - Brian Shuch, MD

UCLA Health/YouTube

1:43

Do I need Genetic Testing for Ichthyosis?

foundation for ichthyosis/YouTube

2:01

What Is Genetic Testing? Understanding the Process and Its Results

uvahealth/YouTube

3:58

How to Understand Your Genetic Testing Results

Breast Cancer Answers®/YouTube

1:00:31

Genetic Testing 101 for People with Rare Diseases

National Organization for Rare Disorders (NORD)/YouTube

2:05

What's the difference between genetic and genomic testing?

Cancer Treatment Centers of America - CTCA/YouTube

Treatment

Physical Therapy

Image by CC0 Creative Commons

Physical Therapy

Image by CC0 Creative Commons

How Might X-Linked Creatine Deficiency Be Treated?

Specialists involved in the care of someone with X-linked creatine may include:

Neurologist
Speech/language pathologist
Occupational therapy
Physical therapy

Source: Genetic and Rare Diseases (GARD) Information Center

Additional Materials (1)

Physical Therapy

Image by mohamed_hassan/Pixabay

Physical Therapy

mohamed_hassan/Pixabay

Statistics

Populations - How Common

Image by geralt/Pixabay

Populations - How Common

Image by geralt/Pixabay

How Common Is X-Linked Creatine Deficiency?

The prevalence of X-linked creatine deficiency is unknown. More than 150 affected individuals have been identified. The disorder has been estimated to account for between 1 and 2 percent of males with intellectual disability.

Source: MedlinePlus Genetics

Related HealthJournals

Genetic Testing

Genetic testing is a type of medical test that identifies changes in chromosomes, genes, or proteins. Over 2000 tests are available. Genetic testing may be done for many reasons, from newborn baby screening to diagnosing certain diseases. Read about why you might consider testing.

Newborn Screening

A newborn infant has screening tests that must be done during the first few days of life. These tests look for serious medical conditions that can cause lifelong health problems or early death. With early diagnosis, treatment can begin right away, before serious problems can occur or become permanent. Get the facts about these tests.

Performance Supplements

A nutritionally adequate diet and plenty of fluids are important for maximizing your physical performance, but you may wonder if dietary supplements could help you train harder, improve performance, or gain a competitive edge. Learn about the effectiveness and safety of ingredients in dietary supplements that are promoted to improve athletic performance.

Share and discuss

Share your story, discuss an issue or get
advice from the community

Create conversation

Sign up here for full access to StoryMD

Get free access to in-depth articles and track your personal health.

Create Free Account Sign In

Share with others

Send this HealthJournal to your friends or across your social medias.

X-Linked Creatine Deficiency

Creatine is needed for the body to store and use energy properly. X-linked creatine deficiency is an inherited disorder that impairs the body's ability to bring creatine into cells. This primarily affects the brain leading to intellectual disability, ranging from mild to severe, and delayed speech development. Explore causes, symptoms, and treatment.

Copy Link