Creatine Transporter Deficiency
What else is it called?
- Creatine transporter defect
- Creatine transporter deficiency
- SLC6A8 deficiency
- SLC6A8-related creatine transporter deficiency
- X-linked creatine deficiency
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What causes it?
This disorder is caused by a problem in the SLC6A8 gene. This gene provides instructions for the production of a protein that carries energy (creatine) to cells in vital muscles and organs in the body, including the brain. This process is needed to ensure that the muscles and organs have enough energy to develop and function properly.
If you have a problem in the SLC6A8 gene, you will not produce enough of the protein required to transport the creatine. Therefore, your body will struggle as it will lack the energy it requires.
A lack of creatine particularly affects your muscles and brain, which are unable to function properly without it. This causes developmental delays in learning, understanding, and speech, and in the muscles needed to walk, sit up, and stand.
How common is it?
Creatine Transporter Deficiency is rare and so its prevalence is currently unknown. However, over 150 cases of the disorder have been reported worldwide.
The disorder tends to affect males more acutely. Females are typically carriers and their symptoms are likely to be much less severe than males. Creatine Transporter Deficiency is estimated to affect between 1% and 2% of males with intellectual disabilities.
What are the signs and symptoms?
Symptoms are closely linked to development, so you may recognise them when typical milestones are missed or delayed. However, there are cases of people being diagnosed in infancy all the way to the age of 66.
Symptoms vary from person to person, but your symptoms will typically include:
- Intellectual disabilities, ranging from mild to severe
- Autistic behaviours
- ADHD behaviours
- Prominent speech and language delays
- Developmental delays in motor skills such as sitting up and walking
- Slow growth
- Muscle weakness
A very small number of people have additional symptoms such as abnormal heart rhythms, a very small head (microcephaly), or prominent facial features including a large forehead and sunken appearance in the middle of the face (midface hypoplasia).
Life expectancy is dependent on the severity of your symptoms, but most people with Creatine Transporter Deficiency are able to live a long life.
How is it diagnosed?
Creatine Transporter Deficiency is diagnosed using specialised urine and blood tests. Your medical team may also carry out genetic testing, and you may also be asked to have an MRI scan to look closer at what is happening in your brain.
Due to the presentation of people with Creatine Transporter Deficiency, it is possible that you will be given a differential diagnosis of autism, ADHD, or learning disability before the disorder is correctly diagnosed.
Creatine Transporter Deficiency is not part of the newborn screening programme in any country. However, screening methods have vastly improved in recent years and the disorder is becoming more widely understood. As a result, professionals expect that most people with the condition will now be diagnosed within the first three years of their lives.
Can it be treated?
There is no known cure for Creatine Transporter Deficiency. However, treatments are available to support you and improve some of the symptoms. As well as doctors, this care may be offered by a team that includes:
- Occupational therapists
- Dieticians Speech therapists
- Physical therapists
The specific team that supports you will primarily depend upon the symptoms you have.
There is currently ongoing research to develop medications for a variety of creatine deficiencies, but there are no medications currently known to help Creatine Transporter Deficiency. However, your medical team may offer medication in relation to some of your symptoms.
Many people with Creatine Transporter Deficiency are expected to live long lives. However, this is typically dependent on the severity of your symptoms. Your medical team will be able to give you more information on your prognosis.
Do my family need to be tested?
Creatine Transporter Deficiency is inherited from your parents through your X chromosome. Every person has two chromosomes – one from your mother and one from your father – that determine our DNA. Everybody receives an X chromosome from their mother. Males receive a Y chromosome from their father and females receive an X chromosome. This is what determines our sex.
Because males only have one X chromosome, if the SLC6A8 gene is faulty, there is no ‘back-up’ from their Y chromosome. This means that they will have Creatine Transporter Deficiency. However, girls with the faulty SLC6A8 gene will have an extra, working gene from their father that will override the faulty gene. They will then become carriers.
Mothers who are carriers have a 25% chance of passing Creatine Transporter Deficiency to their son. There is a 25% chance they will have a daughter who is a carrier, and there is a 50% chance that their child will be born without the faulty gene.
Fathers who are affected by Creatine Transporter Deficiency cannot pass it onto their sons. However, any daughters they have will be carriers of the disorder.
If you think that somebody in your family may be affected by this disorder, or may be a carrier, contact your medical team to explore the possibility of genetic testing so that they can get the support they require.