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Genetics Home Reference: your guide to understanding genetic conditions     A service of the U.S. National Library of Medicine®

Holocarboxylase synthetase deficiency

Reviewed June 2007

What is holocarboxylase synthetase deficiency?

Holocarboxylase synthetase deficiency is an inherited disorder in which the body is unable to use the vitamin biotin effectively. This disorder is classified as a multiple carboxylase deficiency, a group of disorders characterized by impaired activity of certain enzymes that depend on biotin.

The signs and symptoms of holocarboxylase synthetase deficiency typically appear within the first few months of life, but the age of onset varies. Affected infants often have difficulty feeding, breathing problems, a skin rash, hair loss (alopecia), and a lack of energy (lethargy). Immediate treatment and lifelong management with biotin supplements may prevent many of these complications. If left untreated, the disorder can lead to delayed development, seizures, and coma. These medical problems may be life-threatening in some cases.

How common is holocarboxylase synthetase deficiency?

The exact incidence of this condition is unknown, but it is estimated to affect 1 in 87,000 people.

What genes are related to holocarboxylase synthetase deficiency?

Mutations in the HLCS gene cause holocarboxylase synthetase deficiency.

The HLCS gene provides instructions for making an enzyme called holocarboxylase synthetase. This enzyme is important for the effective use of biotin, a B vitamin found in foods such as liver, egg yolks, and milk. Holocarboxylase synthetase attaches biotin to certain enzymes that are essential for the normal production and breakdown of proteins, fats, and carbohydrates in the body. Mutations in the HLCS gene reduce the enzyme's ability to attach biotin to these enzymes, preventing them from processing nutrients properly and disrupting many cellular functions. These defects lead to the serious medical problems associated with holocarboxylase synthetase deficiency.

Related Gene(s)

Changes in this gene are associated with holocarboxylase synthetase deficiency.

  • HLCS

How do people inherit holocarboxylase synthetase deficiency?

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

Where can I find information about diagnosis or management of holocarboxylase synthetase deficiency?

These resources address the diagnosis or management of holocarboxylase synthetase deficiency and may include treatment providers.

  • Baby's First Test (
  • Genetic Testing Registry: Holocarboxylase synthetase deficiency (
  • MedlinePlus Encyclopedia: Pantothenic Acid and Biotin (

You might also find information on the diagnosis or management of holocarboxylase synthetase deficiency in Educational resources and Patient support.

General information about the diagnosis ( and management ( of genetic conditions is available in the Handbook. Read more about genetic testing (, particularly the difference between clinical tests and research tests (

To locate a healthcare provider, see How can I find a genetics professional in my area? ( in the Handbook.

Where can I find additional information about holocarboxylase synthetase deficiency?

You may find the following resources about holocarboxylase synthetase deficiency helpful. These materials are written for the general public.

You may also be interested in these resources, which are designed for healthcare professionals and researchers.

What other names do people use for holocarboxylase synthetase deficiency?

  • Early-Onset Biotin-Responsive Multiple Carboxylase Deficiency
  • Early-Onset Combined Carboxylase Deficiency
  • HLCS deficiency
  • Infantile Multiple Carboxylase Deficiency
  • Multiple Carboxylase Deficiency, Neonatal Form

For more information about naming genetic conditions, see the Genetics Home Reference Condition Naming Guidelines ( and How are genetic conditions and genes named? ( in the Handbook.

What if I still have specific questions about holocarboxylase synthetase deficiency?

Ask the Genetic and Rare Diseases Information Center (

What glossary definitions help with understanding holocarboxylase synthetase deficiency?

aciduria ; alopecia ; autosomal ; autosomal recessive ; biotin ; breakdown ; carboxylase ; cell ; coma ; deficiency ; egg ; enzyme ; gene ; incidence ; inherited ; lethargy ; neonatal ; newborn screening ; recessive ; screening

You may find definitions for these and many other terms in the Genetics Home Reference Glossary.


  • Morrone A, Malvagia S, Donati MA, Funghini S, Ciani F, Pela I, Boneh A, Peters H, Pasquini E, Zammarchi E. Clinical findings and biochemical and molecular analysis of four patients with holocarboxylase synthetase deficiency. Am J Med Genet. 2002 Jul 22;111(1):10-8. (
  • Tang NL, Hui J, Yong CK, Wong LT, Applegarth DA, Vallance HD, Law LK, Fung SL, Mak TW, Sung YM, Cheung KL, Fok TF. A genomic approach to mutation analysis of holocarboxylase synthetase gene in three Chinese patients with late-onset holocarboxylase synthetase deficiency. Clin Biochem. 2003 Mar;36(2):145-9. (


The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? ( in the Handbook.

Reviewed: June 2007
Published: February 8, 2016