Arginine Glycine Amidinotransferase Deficiency
What else is it called?
- AGAT deficiency
- Cerebral creatine deficiency syndrome 3
- Creatine deficiency syndrome due to AGAT deficiency
- GATM deficiency
- L-arginine glycine amidinotransferase deficiency
- L-arginine glycine aminidotransferase deficiency
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What causes it?
This disorder is caused by a problem in the GATM (glycine amidinotransferase) gene. This gene produces the arginine glycine amidinotransferase enzyme, which uses protein to produce a compound called creatine. Creatine is needed to store and release energy in the body.
If you have a problem in the GATM gene, you will not produce enough of the arginine glycine amidinotransferase enzyme. Therefore, you will be unable to produce enough creatine, and this causes energy shortages within the body. This is particularly problematic for large organs, such as the brain, that require a lot of energy to function.
How common is it?
Arginine Glycine Amidinotransferase Deficiency is an extremely rare disorder. As a result, its prevalence is unknown, with less than 20 cases identified. It was first recognised and diagnosed by medical professionals in 2000, so it is still a relatively new disorder, which contribute to the reason why so few cases have been identified so far.
Due to its rarity, it is difficult to say whether the disorder is likely to affect certain populations or groups more than others.
What are the signs and symptoms?
The symptoms of Arginine Glycine Amidinotransferase Deficiency typically begin to appear in infancy. These include:
- Mild to moderate intellectual disabilities
- Delayed speech development
- Delayed motor skills development, such as sitting and walking
- Autistic behaviours, particularly in relation to communication and social interactions
- Seizures, mainly during periods of illness
- Not growing as expected or gaining weight (known as failure to thrive)
- Weakness in the muscles
- Getting tired easily
Some symptoms do not appear until later on in childhood. They will get progressively worse without diagnosis and the appropriate treatment. Following the management plan set out by your medical team can vastly improve your symptoms, however it is much more effective when treatment is commenced in infancy or childhood.
How is it diagnosed?
To diagnose Arginine Glycine Amidinotransferase Deficiency, your medical team will use specialised blood and urine tests. A genetic test will be required to confirm your diagnosis. You may also have an MRI scan to confirm the diagnosis and to measure the creatine levels in your brain.
Arginine Glycine Amidinotransferase Deficiency is commonly misdiagnosed in infants and toddlers as cerebral palsy. Children may also be diagnosed as having autism or a developmental delay.
It is possible that you can have the disorder but not show any symptoms, and so you may only be diagnosed after a member of your family has tested positive. If your sibling has been diagnosed with the disorder, it is important that you get tested as soon as possible so that any treatment you require can begin promptly.
Can it be treated?
Arginine Glycine Amidinotransferase Deficiency can be treated with creatine supplements, which have been particularly effective in improving symptoms for patients who are treated early. It is important to get a diagnosis as early as possible so that treatment is not delayed. Also, if you have a diagnosis, your siblings – especially newborn babies – should be treated to prevent any potential disorder they may have from developing harmful symptoms.
There are also supportive and symptomatic treatments that your medical team may recommend, including physical, occupational, speech, and behaviour therapies. You may also have the support of a neurologist, dietician, and geneticist. The treatments and support you are offered will be dependent on your specific needs.
The prognosis for Arginine Glycine Amidinotransferase Deficiency is currently unclear. The first case identified was in 2000, so there are not yet any long-term case studies from which we can gather information. However, supplement treatment has been very beneficial and works well in significantly reducing symptoms.
Do my family need to be tested?
Arginine Glycine Amidinotransferase Deficiency is an autosomal recessive disorder, which means that it is inherited from both parents, who are carriers of the disorder through their genes.
All genes come in pairs. Carriers of Arginine Glycine Amidinotransferase Deficiency have one working GATM gene and one faulty gene. Children inherit one gene from each parent to make their pair. Whether they have Arginine Glycine Amidinotransferase Deficiency depends on the genes they inherit:
- There is a 50% chance that the child will inherit one faulty and one working gene, which means they will also be a carrier.
- There is a 25% chance that the child will inherit two working genes and not inherit or carry the faulty gene.
- There is a 25% chance that the child will inherit two faulty genes, which means they will have Arginine Glycine Amidinotransferase Deficiency.
If you think somebody in your family may have Arginine Glycine Amidinotransferase Deficiency, or that you may be a carrier, contact your medical team who may refer you for genetic testing.
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