Medium chain acyl dehydrogenase deficiency (MCADD) is a rare inherited disorder where your body cannot metabolise (break down) fat properly.
MCADD can cause drowsiness, lack of energy and diarrhoea, and can put you at risk of complications such as seizures, breathing difficulties and even coma or sudden death (see Symptoms for more information).
Symptoms usually appear during infancy or early childhood, but in rare cases they may not appear until adulthood.
What happens?
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.
People with MCADD cannot break down fatty acids properly, because they lack one of the enzymes needed. This leads to a build-up of medium-chain fats, which can become toxic (see Causes for more information). Because they cannot get energy from fat, they must rely on glucose for their energy.
How common is it?
Around one in 10,000 babies born in the UK has MCADD. Newborn screening throughout England identifies around 60 cases each year.
Around one in 80 healthy people is a carrier of MCADD, but will not have any symptoms. However, if both parents are MCADD carriers, there is a one-in-four chance of their child being born with MCADD.
Outlook
Once diagnosed, MCADD is usually quite straightforward to manage and children can lead healthy, normal lives.
It is managed by eating regular meals and having frequent glucose drinks if the child falls ill, so that their blood glucose level does not fall (see Treatment for more information).
However, if MCADD is not identified and treated early, children may fall into repeated comas with complications including breathing problems, seizures, brain damage or sudden death.
