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Holocarboxylase synthetase deficiency

(HOH-loh-kahr-BAHK-suh-lace • SIN-thuh-tace • di- FISH-uhn-see)

General Condition Information

Other Names

  • Holocarboxylase synthase
  • Holocarboxylase synthase deficiency
  • Holocarboxylase synthetase
  • Holocarboxylase synthetase deficiency (multiple carboxylase deficiency)
  • MCD
  • Multiple carboxylase
  • Multiple carboxylase deficiency
  • Multiple carboxylase deficiency (holocarboxylase sythetase)
  • Multiple CoA carboxylase deficiency

Condition Type

Birth Prevalence

It is estimated that less than 50 babies are born each year with this condition in the United States.

Screening Finding

Elevated C5-OH acylcarnitine

What is Holocarboxylase synthetase deficiency

Holocarboxylase synthetase deficiency is an inherited (genetic) condition that prevents the body from breaking down certain proteins, carbohydrates, and fats.

Holocarboxylase synthetase is an enzyme in your body that adds the vitamin biotin to other enzymes. Adding biotin helps those enzymes break down carbohydrates, proteins, and fats to use them for energy or get rid of them.

If your baby’s holocarboxylase synthetase enzyme is not working well, enzymes that need biotin do not work as well. This condition can be more or less severe depending on how well your baby’s holocarboxylase synthetase enzyme is working.

Breaking down proteins, carbohydrates, and fats for energy allows your body to work properly. When proteins, carbohydrates, and fats are not processed, waste and toxins can build up, and cause damage. If untreated, this damage leads to the signs and symptoms of the condition. In severe cases, this condition can result in brain damage or coma 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:

  • Biotin supplements
  • Careful management during illness

Children who receive early and ongoing treatment for holocarboxylase synthetase deficiency can have healthy growth and development.

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