Medium-chain acyl-CoA dehydrogenase deficiency (MCADD) 

  • Overview

Introduction 

MCADD is caused by an inherited faulty or missing enzyme that the body usually uses to break down fatty acids  

Metabolic disease

Medium-chain acyl-CoA dehydrogenase deficiency (MCADD) is a metabolic disease.

A metabolic disease occurs when something disrupts the body’s processes which obtain energy from food.

A related charity you may find useful is called the Climb Group (Children living with inherited metabolic disease).

Medium-chain acyl-CoA dehydrogenase deficiency (MCADD) is a rare genetic condition in which a person has problems breaking down fatty acids for energy.

This means that if they go for long periods without eating they can experience a range of unpleasant symptoms, such as:

  • feeling very tired and sluggish
  • being sick
  • seizures (fits)

Left untreated MCADD can lead to more serious complications such as coma, brain damage and liver failure and can sometime prove fatal.

Symptoms can be triggered once a baby stopped receiving regular nightly feeds. Though there have been a number of cases where symptoms begin shortly after birth due to an interruption in a new-born baby’s feeding.

Read more about the symptoms of medium-chain acyl-CoA dehydrogenase deficiency.

What causes MCADD?

People with MCADD are born with a faulty or missing enzyme that the body normally uses to break down fatty acids (an enzyme is a type of protein that can cause chemical reactions inside cells).

During long periods between eating, the body breaks down its fat stores to produce energy. Fats are broken down into fatty acids, which are then broken down into shorter and shorter lengths. At each step, energy is released.

Therefore, when people with MCADD go for a long time without eating two harmful effects occur:

  • there is a build-up of medium chain fats inside the body which can have a toxic (poisonous) effect
  • the body then uses its glucose resources as an alternative energy source which can lead to a sudden and severe drop in blood sugar levels (hypoglycaemia)

The faulty or missing enzyme is the result of genetic mutations a child inherits from their parents (the parents themselves are usually unaffected by MCADD).

A genetic mutation is when the instructions found in all living cells becomes scrambled in some way meaning that one or more of the body’s processes does not work properly.

Read more about the causes of medium-chain acyl-CoA dehydrogenase deficiency.

Treating MCADD

There is currently no cure of MCADD so treatment involves making sure that you or your child doesn’t go for long periods without eating

The maximum ‘safe fasting time’ for children who are not ill can vary according to age:

  • babies under the age of four months should not go more than six hours without eating
  • babies between the aged of 4-8 months should not go more than eight hours without eating
  • babies between the ages of 8-12 months should not go more than ten hours without eating
  • all other children (and adults) over the age of one year should not go more than 12 hours without eating

Sick children will need to be fed more frequently.

If you or your child experiences any symptoms of MCADD, there are a number of high-glucose drinks that can be used to boost blood sugar levels.

Read more about the treatment of medium-chain acyl-CoA dehydrogenase deficiency.

Screening

In the past babies with MCADD went undiagnosed until they experienced symptoms – often known as an acute attack or metabolic crisis.

This could often be life-threatening as the parents had no idea what was happening and how to treat the symptoms.

Because of this the NHS introduced a screening programme for MCADD in 2009.  All newborn babies in England are given a blood test that can be used to screen for MCADD.

Read more about diagnosing medium-chain acyl-CoA dehydrogenase deficiency.

Who is affected

MCADD is a rare condition. It is estimated that 1 in every 10,000 babies are born with the condition meaning that around 60 babies are positively screened with MCADD every year in England. Both sexes are equally affected.

Outlook

The outlook for MCADD is usually very good.

The condition is relatively straightforward to manage. Providing that the condition is diagnosed and that dietary recommendations are kept to there is no reason why a child with MCADD cannot live a normal healthy life.

Page last reviewed: 07/02/2012

Next review due: 07/02/2014

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