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

Malonyl-CoA decarboxylase deficiency

Reviewed January 2010

What is malonyl-CoA decarboxylase deficiency?

Malonyl-CoA decarboxylase deficiency is a condition that prevents the body from converting certain fats to energy. The signs and symptoms of this disorder typically appear in early childhood. Almost all affected children have delayed development. Additional signs and symptoms can include weak muscle tone (hypotonia), seizures, diarrhea, vomiting, and low blood sugar (hypoglycemia). A heart condition called cardiomyopathy, which weakens and enlarges the heart muscle, is another common feature of malonyl-CoA decarboxylase deficiency.

How common is malonyl-CoA decarboxylase deficiency?

This condition is very rare; fewer than 30 cases have been reported.

What genes are related to malonyl-CoA decarboxylase deficiency?

Mutations in the MLYCD gene cause malonyl-CoA decarboxylase deficiency. The MLYCD gene provides instructions for making an enzyme called malonyl-CoA decarboxylase. Within cells, this enzyme helps regulate the formation and breakdown of a group of fats called fatty acids. Many tissues, including the heart muscle, use fatty acids as a major source of energy.

Mutations in the MLYCD gene reduce or eliminate the function of malonyl-CoA decarboxylase. A shortage of this enzyme disrupts the normal balance of fatty acid formation and breakdown in the body. As a result, fatty acids cannot be converted to energy, which can lead to characteristic features of this disorder including low blood sugar and cardiomyopathy. Byproducts of fatty acid processing build up in tissues, which also contributes to the signs and symptoms of malonyl-CoA decarboxylase deficiency.

Related Gene(s)

Changes in this gene are associated with malonyl-CoA decarboxylase deficiency.


How do people inherit malonyl-CoA decarboxylase 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 malonyl-CoA decarboxylase deficiency?

These resources address the diagnosis or management of malonyl-CoA decarboxylase deficiency and may include treatment providers.

  • Baby's First Test (
  • Genetic Testing Registry: Deficiency of malonyl-CoA decarboxylase (

You might also find information on the diagnosis or management of malonyl-CoA decarboxylase 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 malonyl-CoA decarboxylase deficiency?

You may find the following resources about malonyl-CoA decarboxylase 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 malonyl-CoA decarboxylase deficiency?

  • deficiency of malonyl-CoA decarboxylase
  • malonic aciduria
  • malonyl-coenzyme A decarboxylase deficiency
  • MCD deficiency

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 malonyl-CoA decarboxylase deficiency?

Ask the Genetic and Rare Diseases Information Center (

What glossary definitions help with understanding malonyl-CoA decarboxylase deficiency?

acids ; aciduria ; autosomal ; autosomal recessive ; breakdown ; cardiomyopathy ; cell ; CoA ; coenzyme A ; deficiency ; enzyme ; fatty acids ; gene ; hypoglycemia ; hypotonia ; inherited ; muscle tone ; newborn screening ; oxidation ; recessive ; screening

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


  • de Wit MC, de Coo IF, Verbeek E, Schot R, Schoonderwoerd GC, Duran M, de Klerk JB, Huijmans JG, Lequin MH, Verheijen FW, Mancini GM. Brain abnormalities in a case of malonyl-CoA decarboxylase deficiency. Mol Genet Metab. 2006 Feb;87(2):102-6. Epub 2005 Nov 4. (
  • FitzPatrick DR, Hill A, Tolmie JL, Thorburn DR, Christodoulou J. The molecular basis of malonyl-CoA decarboxylase deficiency. Am J Hum Genet. 1999 Aug;65(2):318-26. (
  • Sacksteder KA, Morrell JC, Wanders RJ, Matalon R, Gould SJ. MCD encodes peroxisomal and cytoplasmic forms of malonyl-CoA decarboxylase and is mutated in malonyl-CoA decarboxylase deficiency. J Biol Chem. 1999 Aug 27;274(35):24461-8. (
  • Salomons GS, Jakobs C, Pope LL, Errami A, Potter M, Nowaczyk M, Olpin S, Manning N, Raiman JA, Slade T, Champion MP, Peck D, Gavrilov D, Hillman R, Hoganson GE, Donaldson K, Shield JP, Ketteridge D, Wasserstein M, Gibson KM. Clinical, enzymatic and molecular characterization of nine new patients with malonyl-coenzyme A decarboxylase deficiency. J Inherit Metab Dis. 2007 Feb;30(1):23-8. Epub 2006 Dec 20. (


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: January 2010
Published: February 8, 2016