A rare inherited condition in which there is lack of an enzyme needed to convert fats to energy
- Present at birth
- Due to an abnormal gene inherited from both parents
- Gender and lifestyle are not significant factors
The abbreviation for medium-chain acyl CoA dehydrogenase deficiency, MCADD is a rare hereditary metabolic disorder in which there is a lack of an enzyme needed to completely convert fats to energy. The body’s first source of energy is glucose (a type of sugar), which circulates in the blood. When this glucose is used up – during a long period without food or during an illness, for example – fats from the body’s stores are broken down to produce energy. This fat breakdown occurs in several stages, each stage requiring a different enzyme. People with MCADD lack one of these enzymes and so cannot break down fats completely. As a result, there is a build up of partly broken down fats (medium-chain fats), which can accumulate to toxic levels. In addition, because the body’s glucose is used up, the blood glucose levels may drop to a dangerously low level.
The underlying cause of MCADD is an abnormal gene on chromosome 1. This gene is carried by about 1 in 80 people in the UK and is inherited in an autosomal recessive manner (see Gene disorders), which means that two copies of the abnormal gene, one from each parent, are necessary to develop MCADD. Carriers have only one copy of the abnormal gene and do not have any symptoms. MCADD is rare, affecting about 1 in 10,000 babies.
What are the symptoms?
Typically, symptoms do not appear until between 3 months and 3 years after birth and are often triggered by an infection, a period of poor feeding, or when a baby starts to feed less at night. Initial symptoms may include:
Irritability and sleepiness.
Vomiting and diarrhoea.
Without prompt treatment, breathing problems, seizures, and unconsciousness may develop. In some cases there may be brain damage, heart failure, or even death.
What might be done?
MCADD can be detected shortly after birth as part of the routine blood spot screening tests. The condition is treated by diet. There is no specific diet but the disorder requires close monitoring of the child to determine “safe” time periods between meals, and a strict feeding schedule to ensure that an affected child does not go for long periods without food. However, during an illness, glucose supplements, as well as a regular diet, may be necessary. If a child is unable to eat or drink normally, it may be necessary to admit him or her to hospital for intravenous feeding. Dietary treatment is usually lifelong but with proper dietary management children with MCADD usually develop normally and lead healthy, active lives.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.
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