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Beta-ketothiolase deficiency

(BAY-tuh-KEE-toh-THIE-o-lace • di- FISH-uhn-see)

General Condition Information

Other Names

  • 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
  • βeta-ketothiolase deficiency

Condition Type

Birth Prevalence

It is unknown how many babies are born with this rare condition each year in the United States.

Screening Finding

Elevated C5-OH acylcarnitine

What is beta-ketothiolase deficiency

Beta-ketothiolase deficiency is an inherited (genetic) condition that prevents the body from breaking down certain proteins and fats.

“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.

If untreated, this damage leads to the signs and symptoms of the condition. In severe cases, this condition can result in coma or death unless treated early.

Newborn Screening and Follow-Up

Condition Details

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.

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