General Condition Information
- 2-methyl-3-hydroxybutyric acidemia
- 3-ketothiolase deficiency
- 3-KTD deficiency
- 3-oxothiolase deficiency
- Alpha-methylacetoacetic aciduria
- B-ketothiolase deficiency
- Beta ketothiolase
- Beta ketothiolase (Mitochondrial acetyl-CoA thiolase deficiency)
- Beta ketothiolase deficiency
- Beta-Ketothiolase Deficiency / Mitochondrial Acetoacetyl-CoA Thiolase Deficiency
- MAT deficiency
- Mitochondrial acetoacetyl-CoA thiolase deficiency
- T2 deficiency
- β ketothiolase deficiency
- β-ketothiolase deficiency
- βeta-ketothiolase deficiency
It is unknown how many babies are born with this rare condition each year in the United States.
What is Beta-ketothiolase deficiency
“ACAT1” is an enzyme that helps your body digest a part of proteins called isoleucine. ACAT1 breaks isoleucine into smaller pieces that your body can either use or remove. It also helps you process ketones, which are important for energy that your baby’s body and brain need when stressed or in between feeding.
If your baby’s ACAT1 enzyme is not working well, their body has trouble processing proteins with isoleucine and fats. Waste, including toxins, can build up. These toxins can damage your baby’s tissues and organs, especially the brain.
Newborn Screening and Follow-Up
Newborn screening for beta-ketothiolase deficiency is done using a small amount of blood collected from your baby’s heel. To learn more about this process, visit the Blood Spot Screening page.
During screening, a special machine measures how much of certain substances (called acylcarnitines) are in your baby’s blood. Your body makes these substances when it breaks down food. Babies with high levels of these substances might have beta-ketothiolase deficiency.
If your baby’s blood spot screening result for beta-ketothiolase deficiency is out-of-range, your baby’s health care provider will contact you. Together, you will discuss next steps and follow-up plans.
An out-of-range screening result does not mean that your baby definitely has the condition. It does mean that your baby needs more follow-up testing. An out-of-range result can mean that your baby has one of several possible conditions. It is important to do follow-up testing to correctly identify the condition causing your baby’s result. To learn more about screening results, visit the Blood Spot Screening Results page.
Your baby may need the following tests after an out-of-range screening result:
- Blood and/or urine tests
- Genetic testing using a blood sample
You should complete any recommended follow-up testing as soon as possible. Babies with this condition can have serious health problems soon after birth if they are not diagnosed and treated quickly.
False-positive newborn screening results for this condition are rare. Babies who are born early (premature) may have out-of-range results.
Some babies may have a false-positive result for beta-ketothiolase deficiency because their mother has high acylcarnitine levels. These babies do not have and will not develop beta-ketothiolase deficiency. More testing on both mom and baby will determine who has high acylcarnitine levels.
Newborn screening helps babies lead healthier lives. If your baby has an out-of-range result, follow up with your health care provider quickly. It is important to follow their instructions. Your baby may need to get treatment right away, even if they are not showing signs or symptoms. In some cases, your baby’s health care provider may decide it is best to watch (monitor) your baby to decide next steps. Careful monitoring and early treatment will help your baby stay as healthy as possible.
Signs of beta-ketothiolase deficiency often appear when a baby is about 1 year old. However, they can start as early as six months old or as late as 2 years old.
Signs of the condition may include the following:
The condition is caused by a change in the ACAT1 gene. This gene gives your body instructions for making the ACAT1 enzyme, which helps you digest certain proteins and fats.
Without a working ACAT1 gene, your baby cannot make enough working ACAT1 enzyme needed to properly break down certain proteins and fats. As a result, harmful toxins can build up in their body.
- Beta-ketothiolase deficiency is an autosomal recessive condition. Babies inherit the condition when each parent passes down a nonworking ACAT1 gene to their baby. Only babies with two nonworking ACAT1 genes—one from the mom and one from the dad—have this condition.
- People with one working copy and one nonworking copy of the ACAT1 gene are called carriers.
- Carriers do not have or develop the condition. However, they may pass down a nonworking copy of the gene to their children.
- If two parents are carriers of a nonworking copy of the ACAT1 gene, they have a 1 in 4 chance of having a child with beta-ketothiolase deficiency.
- Carriers for beta-ketothiolase deficiency often do not know they are carriers before having a child with the condition. In most cases, families have no history of the condition until the birth of a child with beta-ketothiolase deficiency.
- Parents who already have a child with beta-ketothiolase deficiency still have a 1 in 4 chance of having another child with beta-ketothiolase deficiency. This 1 in 4 chance stays the same for all future children.
- Genetic counselors and medical geneticists can help families learn about this condition and the chance of having children with it. Visit the National Society of Genetic Counselors to find a genetic counselor and the American College of Medical Genetics and Genomics to find a medical geneticist.
Treatment and Management
It is important to talk to your health care provider about which treatment(s) are best for your baby. The goal of treatment is to prevent the health problems caused by this condition.
Treatments may include the following:
- Low-protein diet
- Frequent feedings to avoid long periods without food
- L-carnitine supplements
- Bicitra (a medical supplement to balance acid levels in the blood)
Children who receive early and ongoing treatment for beta-ketothiolase deficiency can have healthy growth and development.