Acyl-coa dehydrogenase, medium-chain, deficiency of

Symptoms

What are the main symptoms of medium-chain acyl-CoA dehydrogenase deficiency (MCAD)?

Infants with medium-chain acyl-CoA dehydrogenase (MCAD) deficiency usually appear normal at birth. Symptoms usually appear somewhere between 3 and 24 months of age, although some infants become sick within a couple days of birth. Sometimes, symptoms first appear later in childhood by the age of 6 or, rarely, as adults. Symptoms usually first appear after an infant or child does not eat for an extended period of time, between 6 to 12 hours depending on their ages. This can occur when they sleep overnight without feeding or during an illness like the flu, a cold, or an ear infection. The body normally gets its energy from a sugar called glucose, but in times of diet or not eating for a period of time, stress or illness, the body may use up glucose and instead uses alternative substances for energy, specifically fats. Because of a deficiency in an enzyme, infants, children and adults with MCAD deficiency cannot breakdown these fats, which build up in the cells and tissues of the body and interfere with other chemical processes in the body.

Common symptoms include vomiting, nausea, diarrhea, and very low energy levels so that infants are very sleepy or hard to wake up. The liver may be abnormally large, a condition called hepatomegaly. If individuals are tested during an episode they may have low blood sugar, which is called hypoglycemia. Severe episodes can lead to problems breathing, seizures, brain damage, coma and sudden death because the heart may stop.

As long as MCAD deficiency is properly diagnosed (as with newborn screening programs) and treated by frequent feedings to avoid long periods without food (fasting), the prognosis of the disorder is excellent and most people with have normal lifespans.

References
  • Medium-Chain Acyl-Coenzyme A Dehydrogenase Deficiency" Genetics Home Reference website. https://ghr.nlm.nih.gov/condition/medium-chain-acyl-coa-dehydrogenase-deficiency
  • Roe CR. MCAD: Medium Chain acyl CoA Dehydrogenase - Information for Families. The FOD Family Support Group website. http://www.fodsupport.org/mcad-fam.htm
  • Matern D, Rinaldo P. Medium-Chain Acyl-Coenzyme A Dehydrogenase Deficiency. GeneReviews website. https://www.ncbi.nlm.nih.gov/books/NBK1424/#mcad
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If you have MCAD deficiency will you always show symptoms?

What is a metabolic crisis in medium-chain acyl-CoA dehydrogenase (MCAD) deficiency?

If you have MCAD deficiency will you always show symptoms?

Some people may have changes in the ACADM gene that cause a milder form of medium-chain acyl-CoA dehydrogenase (MCAD) deficiency. These people can go their entire lives without ever developing symptoms of the disorder. However, they are at risk under specific circumstances of having a metabolic episode. There are times when people develop symptoms of MCAD deficiency for the first time as adults.

References
  • Matern D, Rinaldo P. Medium-Chain Acyl-Coenzyme A Dehydrogenase Deficiency. GeneReviews website. https://www.ncbi.nlm.nih.gov/books/NBK1424/#mcad
  • Roe CR. MCAD: Medium Chain acyl CoA Dehydrogenase - Information for Families. The FOD Family Support Group website. http://www.fodsupport.org/mcad-fam.htm
What is a metabolic crisis in medium-chain acyl-CoA dehydrogenase (MCAD) deficiency?

People with medium-chain acyl-CoA dehydrogenase (MCAD) deficiency are at risk of having an episode of metabolic crisis or metabolic decompensation. These episodes can occur when a person does not for a period of time or during times of higher energy demands for the body. The time gap is defined as 12 hours or more in children over 2 years of age (this applies to teenagers and adults as well); up to 10 hours during the second year of life; and up to about eight hours for infants between 6 and 12 months old. People with MCAD deficiency lack an enzyme that is necessary to break down fats for energy. Normally, the body uses a common sugar called glucose for energy, but when a person hasn't eaten for a long time, the body may not have enough glucose and instead starts to use fats for energy. People with MCAD deficiency cannot breakdown (metabolize) these fats to use for energy. The buildup of these fats inhibits or affects other chemical processes in the body and leads to lots of problems.

Common symptoms include vomiting, nausea, diarrhea, and very low energy levels so that infants are very sleepy or hard to wake up. The liver may be abnormally large, a condition called hepatomegaly. If individuals are tested during an episode they may have low blood sugar, which is called hypoglycemia. Severe episodes can lead to problems breathing, seizures, brain damage, coma and sudden death because the heart may stop.

If people with MCAD deficiency avoid going long periods without eating and take precautions and proper care of themselves, they can avoid having a metabolic crisis.

References
  • Roe CR. MCAD: Medium Chain acyl CoA Dehydrogenase - Information for Families. The FOD Family Support Group website. http://www.fodsupport.org/mcad-fam.htm
  • Matern D, Rinaldo P. Medium-Chain Acyl-Coenzyme A Dehydrogenase Deficiency. GeneReviews website. https://www.ncbi.nlm.nih.gov/books/NBK1424/#mcad

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