Conditions Beta-Ketothiolase Deficiency

Beta-ketothiolase deficiency (BKT) is an inherited condition in which the body is unable to break down certain proteins. People with the condition are also unable to produce ketone bodies, substances that help the body store energy. BKT is considered an organic acid condition because it can lead to a dangerous amount of organic acids and toxins in the body. Early detection and treatment can often prevent the severe outcomes of this condition.

Condition Type

Organic Acid Conditions


Though the exact number of people affected is unknown, beta-ketothiolase deficiency is estimated to affect fewer than one in one million newborns.

Also known as

  • BKT
  • Ketone utilization disorder
  • Mitochondrial acetoacetyl-CoA thiolase deficiency
  • T2 deficiency
  • 2-alpha-methyl-3-hydroxybutyricacidemia
  • 3-alpha-ketothiolase deficiency
  • 3-alpha-ktd deficiency
  • 3-alpha-oxothiolase deficiency
  • B-ketothiolase deficiency alpha-methylacetoacetic aciduria
  • 3-Ketothiolase deficiency
  • MAT deficiency
  • 3-methylhydroxybutyric acidemia
  • Mitochondrial 2-methylacetoacetyl-CoA thiolase deficiency-potassium stimulated

Follow-Up Testing

Your baby’s doctor may ask you if your baby is showing any of the signs of BKT (see Early Signs below). If your baby has certain signs, your doctor may suggest starting immediate treatment.

If your baby’s newborn screening result for beta-ketothiolase deficiency (BKT) was out of the normal range, your baby’s doctor or the state screening program will contact you to arrange for your child to have additional testing. It is important to remember that an out-of-range screening result does not necessarily mean that your child has the condition. An out-of-range result may occur because the initial blood sample was too small or the test was performed too early. However, as a few babies do have the condition, it is very important that you go to your follow-up appointment for a confirmatory test. Because the harmful effects of untreated BKT can occur within days after birth, follow-up testing must be completed as soon as possible to determine whether or not your baby has the condition.

Follow-up testing will involve checking your baby’s urine and blood samples for harmful levels of acids and toxins. Certain acids and toxins build up in the body when a child has an organic acid condition, so finding out the levels of these substances in your baby’s body can help doctors determine if your child has a condition. High levels of C5-OH acylcarnitine in the blood and organic acids in the urine might be a sign that your baby has BKT. Sometimes follow-up testing may include testing a very small sample of skin.

About Beta-Ketothiolase Deficiency

Early Signs

Signs of beta-ketothiolase deficiency (BKT) usually start around 1 year of age, though this can range from 6 months to 2 years.

Signs of BKT include:

  • Sleeping longer or more often
  • Tiredness
  • Vomiting
  • Diarrhea
  • Fever
  • Poor appetite
  • Breathing trouble

Many of these signs may occur when your baby eats foods that their body cannot break down. They can be triggered by long periods of time without eating, illnesses, and infections.

If your baby shows any of these signs, be sure to contact your baby’s doctor immediately.


Dietary Treatment

The most important treatment for your baby is a carefully planned diet. Your baby will need a restricted diet in order to avoid too many harmful proteins. A nutritionist or dietician can help you plan a low-protein diet that still gives your baby the nutrients they need for healthy development.

Eating often will also help prevent your baby from experiencing many of the signs mentioned in the Early Signs section. Illnesses and infections can also trigger these signs.

Supplements and Medications

Supplements can also help balance your baby’s digestive system. L-carnitine is a natural substance, but your baby’s body might not make enough of it. L-carnitine supplements can help remove toxic substances from the body. Your baby’s doctor will need to write a prescription for these supplements.

Bicitra is another medical supplement that your baby’s doctor might prescribe. Bicitra helps balance the acid levels in the blood. Babies with BKT have high levels of acid in their blood. While it is normal to have some acid in the blood, very high acid levels can be toxic.

Expected Outcomes

With early treatment, your baby can have healthy growth and development.

There are some cases where children show signs of beta-ketothiolase deficiency (BKT) even with treatment. However, these signs usually decrease with age.

If BKT is not treated, children can develop intellectual disabilities and seizures.


The enzymes in your baby’s body help break down foods. Enzymes break down proteins into their building blocks, amino acids. Other enzymes then break down the amino acids.

In beta-ketothiolase deficiency (BKT), your baby’s body either does not make enough or makes non-working mitochondrial acetoacyl-CoA thiolase (MAT) enzymes. MAT is in charge of breaking down the amino acid isoleucine. If MAT does not work, then isoleucine cannot be digested and harmful substances build up in the body.

BKT is an autosomal recessive genetic condition. This means that a child must inherit two copies of the non-working gene for BKT, one from each parent, in order to have the condition. The parents of a child with an autosomal recessive condition each carry one copy of the non-working gene, but they typically do not show signs and symptoms of the condition. While having a child with BKT is rare, when both parents are carriers, they can have more than one child with the condition. Learn more about autosomal recessive inheritance.

Support for Beta-Ketothiolase Deficiency

Support Services

Support groups can help connect families who have a child or other family member affected with beta-ketothiolase deficiency with a supportive community of people who have experience and expertise in living with the condition. These organizations offer resources for families, affected individuals, health care providers, and advocates.

Accessing Care

Work with your baby’s health care provider to determine the next steps for your baby’s care. Your baby’s doctor may help you coordinate care with a physician who specializes in metabolism, a dietician who can help plan your child’s specialized diet, or other medical resources in your community. Some children with beta-ketothiolase deficiency (BKT) have developmental delays. If you think that your baby is not meeting their developmental milestones, ask your baby’s doctor about the next steps in accessing a developmental evaluation and care.

Because BKT is a genetic condition, you may want to talk with a genetics specialist. A genetic counselor or geneticist can help you understand the causes of the condition, discuss genetic testing for BKT, and understand what this diagnosis means for other family members and future pregnancies. Speak with your baby’s doctor about getting a referral. The Clinic Services Search Engine offered by the American College of Medical Genetics and Genomics and the Find a Genetic Counselor tool on the National Society of Genetic Counselors (NSGC) website are two good resources for you or your baby's health care provider to use to identify local specialists.

Families' Experiences

Olivia is a young girl with beta-ketothiolase deficiency. Though she has had a few hospitalizations, she is doing well now, and her family is optimistic. You can read Olivia’s story on the Save Babies Through Screening website.

References & Sources

Visit MedlinePlus Genetics for more condition information

Visit the Screening, Technology And Research in Genetics (STAR-G) Project for more information on BKT

ACT Sheets

Healthcare professionals can learn more about confirmatory testing by reading the American College of Medical Genetics and Genomics' Algorithm for Diagnosis and ACT Sheet, a guide for follow-up after newborn screening. You can visit this page of the ACMG website here.

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