MCAD deficiency

Medium-chain acyl-CoA dehydrogenase deficiency (MCAD deficiency) is a rare, inherited disease where the body is unable to break down fat properly.

MCAD deficiency can cause lethargy and a lack of energy and can lead to serious complications such as seizures, coma and even death.

What exactly happens?

If one doesn't eat for a long time, the body will burn body fat in order to produce energy. Body fat is broken down to fatty acids and those fatty acids are in their turn broken down to shorter fatty acids until they are completely broken down or metabolised. With each step some energy is released.
People with MCAD deficiency cannot break down fatty acids in a normal way because one of the enzymes necessary for this is not functioning properly. This enzyme is called the MCAD enzyme.
As a result medium chain fatty acids are accumulated in the body. If the body wants to break down fat quickly (because one hasn't eaten in a while or has an infection) then a high concentration of medium chain fatty acids is accumulated. This is poisonous, and can lead to serious complications.
At the same time these people cannot get energy from breaking down medium chain fats, so they are mostly reliant on sugars for their energy production. A lack of energy can in its turn cause serious complications such as low blood sugar.
See the chapter on metabolism for more information.


MCAD deficiency is an inborn, inherited disease.
A baby has a 25 % chance of inheriting the disease from his parents if both parents are carriers of the disease.
See the chapter on genetics for more information.


In Belgium every newborn child is screened for a number of inherited diseases, among which MCAD deficiency.
If it is suspected that a baby has MCAD deficiency there are some other examinations possible to confirm the diagnosis.
See the chapter on diagnosis for more information.

Outlook and treatment

Once the diagnosis is confirmed, patients with MCAD deficiency can live a relatively normal life as long as they take a few simple precautions.
They shouldn't go too long without eating and should be put on a healthy, low fat diet.
Some extra care is necessary in case of illness and/or vomiting. In that case they should be admitted to the hospital to be treated with IV glucose.
See the chapter on treatment for more information.

The information on this website is a summary of information that is publicly available on other websites as well as information from books for sale on the internet and in public book stores.
The content of this website is not validated by doctors, scientists or geneticists.

This page was last modified on 20 February 2011