Medium chain acyl-CoA dehydrogenase deficiency (“MCADD”)

MCADD is a rare genetic metabolic disorder.  It is a type of fatty acid oxidation disorder.  MCADD is estimated to affect one (1) in every seventeen thousand (17,000) people.  

Let’s Begin with the Basics….

The human body needs three primary nutrients in order to function: (1) Carbohydrates; (2) Proteins; and (3) Fats.  Our digestive system breaks each of these nutrients down into simpler compounds that our body uses.  Carbohydrates are broken down into glucose, which supplies our cells with energy.  Proteins break down into amino acids.  Fats are broken down into fatty acids.  

After we eat a meal, carbohydrates are broken down into glucose, therefore our blood sugar rises.  This signals a release of insulin into the bloodstream.  The insulin helps glucose enter our cells, which creates energy.  If all of the glucose is not needed for energy, our body creates a “glucose store” in the liver and in fat cells.  Then, during periods of fasting (i.e., in between meals when we do not eat), our body uses the glucose store (glycogen) for energy.  When glycogen is depleted, fat stores can also be used for energy.  However, in those individuals diagnosed with Medium chain acyl-CoA dehydrogenase disorder, the body lacks an enzyme necessary to break down the fatty acid to produce energy.  

What is MCADD?

Medium chain acyl-CoA dehydrogenase is an enzyme that is necessary for the breakdown (oxidation) of medium chain fatty acids found in fats.  Those affected by MCADD either lack this enzyme or have an insufficient amount of the enzyme, thus are unable to properly oxidize medium chain fatty acids.   Therefore, the body’s inability to oxidize the medium chain fatty acids limits the body’s use of fat for energy.  The inability to oxidize the medium chain fatty acids could also lead to an accumulation of fatty acids causing damage to the liver and brain.  

This can lead to a metabolic crisis.  

The Genetics behind the Disorder

MCADD is an inherited autosomal recessive disorder.  For an individual to have MCADD, this means that both parents must have a single non-working gene for MCADD.  The non-working gene is passed to the child by each parent, thus resulting in the child having MCADD.  

Mutations of the ACADM gene cause MCADD.  The ACADM gene is responsible for the instructions for making the medium-chain acyl-CoA dehydrogenase enzyme.  More than 80 mutations of the gene have been found.  


U.S. National Library of Medicine

National Organization for Rare Disorders


Genetic Metabolic Dietitians International

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