What is Medium-Chain Acyl-CoA Dehydrogenase Deficiency?

Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is an inherited metabolic disorder in which fats cannot be broken down into energy to fuel the body. It is part of a group of disorders called fatty acid oxidation defects and is caused by harmful genetic changes in the ACADM gene. These changes result in a buildup of harmful fatty acids that can accumulate in body tissues and cause damage to the brain, liver, and other organs.

For most individuals with MCAD deficiency, symptoms first appear in infancy or early childhood and can be triggered by long periods without eating (fasting) or by illness. Symptoms include vomiting, lack of energy, low blood sugar, and an enlarged liver. Without treatment, symptoms can quickly develop into life-threatening problems including seizures, breathing problems, brain damage, coma, and death. A small percentage of sudden infant death syndrome (SIDS) is likely due to undiagnosed MCAD deficiency. In some cases, symptoms may not appear until late childhood or adulthood and can be milder.

Additional considerations for carriers

Carriers of MCAD deficiency do not typically show symptoms of the disease. However, there is increased risk of serious pregnancy complications, particularly in the third trimester, in individuals carrying a fetus affected with MCAD deficiency. These complications may include acute fatty liver disease and a life-threatening condition called HELLP syndrome which presents with headache, nausea, swelling, and chest pain. An individual whose pregnancy may be affected by MCAD deficiency should speak with their physician for recommendations and may benefit from consultation with a high-risk physician.

How common is Medium-Chain Acyl-CoA Dehydrogenase Deficiency?

The incidence of MCAD deficiency in the population is 1 in 14,000 to 1 in 25,000 births. The incidence of MCAD deficiency is more common among individuals of Northern European descent.

How is Medium-Chain Acyl-CoA Dehydrogenase Deficiency treated?

The key treatment for individuals with MCAD deficiency is to avoid fasting. Infants must be frequently fed a formula low in fat but high in carbohydrates. For children and adults, consuming cornstarch can also provide a sustained release of energy and allow for longer gaps between meals. If an individual is unable to eat or drink food on their own, it may be necessary to give them glucose by intravenous fluids.

What is the prognosis for an individual with Medium-Chain Acyl-CoA Dehydrogenase Deficiency?

Early diagnosis and dietary management are crucial for the best outcome. If dietary management starts early (especially before the onset of symptoms) and is consistent, individuals with MCAD deficiency have a good prognosis with normal or near-normal lifespan. In undiagnosed and untreated cases of MCAD deficiency, symptoms can quickly cause irreversible damage or even lead to death.

Other names for
medium-chain acyl-CoA dehydrogenase deficiency

  • ACADM deficiency
  • Carnitine deficiency secondary to medium-chain acyl-CoA dehydrogenase deficiency
  • Deficiency of medium-chain acyl-CoA dehydrogenase
  • MCADH deficiency
  • Medium chain acyl-coenzyme A dehydrogenase deficiency


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