Children and Youth with Special Health Needs (CYSHN)
Medium-chain acyl-CoA dehydrogenase deficiency (MCAD)
- What is MCAD?
- What causes MCAD?
- What causes the MCAD enzyme to be absent or not working correctly?
- How is MCAD inherited?
- Is genetic testing available?
- What other testing is available?
- Can you test during pregnancy?
- Can other members of the family have MCAD or be carriers?
- Can other family members be tested?
- How many people have MCAD?
- Does MCAD happen more often in a certain ethnic group?
- Does MCAD go by any other names?
- What is the treatment for MCAD?
- What happens when MCAD is treated?
- If MCAD is not treated, what problems occur?
This fact sheet contains general information about MCAD. Every child is different and some of this information may not apply to your child specifically. Certain treatments may be recommended for some children but not others. Children with MCAD should be followed by a metabolic doctor in addition to their primary doctor.
What is MCAD?
MCAD stands for “medium chain acyl-CoA dehydrogenase deficiency”. It is one type of fatty acid oxidation disorder. People with MCAD have problems breaking down fat into energy for the body.
Fatty Acid Oxidation Disorders:
Fatty acid oxidation disorders (FAODs) are a group of rare inherited conditions. They are caused by enzymes that do not work properly.
A number of enzymes are needed to break down fats in the body (a process called fatty acid oxidation). Problems with any of these enzymes can cause a fatty acid oxidation disorder. People with FAODs cannot properly break down fat from either the food they eat or from fat stored in their bodies.
The symptoms and treatment vary between different FAODs. They can also vary from person to person with the same FAOD. See the fact sheets for each specific FAOD.
FAODs are inherited in an autosomal recessive manner and affect both males and females.
What causes MCAD?
MCAD occurs when an enzyme, called “medium chain acyl-CoA dehydrogenase” (MCAD), is either missing or not working properly. This enzyme's job is to break down certain fats in the food we eat into energy. It also breaks down fat already stored in the body.
Energy from fat keeps us going whenever our bodies run low of their main source of energy, a type of sugar called glucose. Our bodies rely on fat when we don't eat for a stretch of time - like when we miss a meal or when we sleep.
When the MCAD enzyme is missing or not working well, the body cannot use certain types of fat for energy, and must rely solely on glucose. Although glucose is a good source of energy, there is a limited amount available. Once the glucose has been used up, the body tries to use fat without success. This leads to low blood sugar, called hypoglycemia, and to the build up of harmful substances in the blood.
Genes tell the body to make various enzymes. People with MCAD have a pair of genes that do not work correctly. Because of the changes in this pair of genes, the MCAD enzyme either does not work properly or is not made at all.
How is MCAD inherited?
MCAD is inherited in an autosomal recessive manner. It affects both boys and girls equally.
Everyone has a pair of genes that make the MCAD enzyme. In children with MCAD, neither of these genes works correctly. These children inherit one non-working gene for the condition from each parent.
Parents of children with MCAD rarely have the disorder. Instead, each parent has a single non-working gene for MCAD. They are called carriers. Carriers do not have MCAD because the other gene of this pair is working correctly. When both parents are carriers, there is a 25% chance in each pregnancy for the child to have MCAD. There is a 50% chance for the child to be a carrier, just like the parents. And, there is a 25% chance for the child to have two working genes.
Genetic counseling is available to families who have children with MCAD. Genetic counselors can answer your questions about how MCAD is inherited, choices during future pregnancies, and how to test other family members. Ask your doctor about a referral to a genetic counselor.
Is genetic testing available?
Genetic testing for MCAD can be done on a blood sample. Genetic testing, also called DNA testing, looks for changes in the pair of genes that cause MCAD. In many children with MCAD, both gene changes can be found. However, in other children, only one or neither of the two gene changes can be found, even though we know they are present.
DNA testing is not necessary to diagnose your child. It can be helpful for carrier testing or prenatal diagnosis, discussed below.
What other testing is available?
MCAD can also be confirmed either by a blood test called an acylcarnitine profile or an enzyme test on a skin sample. Talk to your doctor or your genetic counselor if you have questions about testing for MCAD.
If both gene changes have been found in your child with MCAD, DNA testing can be done during future pregnancies. The sample needed for this test is obtained by either CVS or amniocentesis.
If DNA testing would not be helpful, an enzyme test can be done during pregnancy on cells from the fetus. Again, the sample needed for this test is obtained by either CVS or amniocentesis.
Parents may either choose to have testing during pregnancy or wait until birth to have the baby tested. A genetic counselor can talk to you about your choices and answer questions about prenatal testing or testing your baby after birth.
Can other members of the family have MCAD or be carriers?
The brothers and sisters of a baby with MCAD have a chance of being affected, even if they have had no symptoms. Finding out whether other children in the family have MCAD is important because early treatment may prevent serious health problems. Talk to your doctor or genetic counselor about testing your other children for MCAD.
Brothers and sisters who do not have MCAD still have a chance to be carriers like their parents. Except in special cases, carrier testing should only be done on people over 18 years of age.
Each of the parents' brothers and sisters has a 50% chance to be an MCAD carrier. It is important for other family members to be told that they could be carriers. There is a small chance they are also at risk to have children with MCAD.
When both parents are carriers, newborn screening results are not sufficient to rule out MCAD in a newborn baby. In this case, special diagnostic testing should be done in addition to newborn screening.
During pregnancy, women carrying fetuses with MCAD may be at increased risk to develop serious medical problems. Some women carrying fetuses with Fatty Acid Oxidation Disorders have developed:
- excessive vomiting
- abdominal pain
- high blood pressure
- abnormal fat storage in the liver
- severe bleeding
All women with a family history of MCAD should share this information with their obstetricians and other health care providers before and during any future pregnancies. Knowing about these risks allows better medical care and early treatment if needed.
Can other family members be tested?
Brothers and sisters can be tested for MCAD using DNA testing or other special tests.
If both gene changes have been found in your child with MCAD, other family members can have DNA testing to see if they are carriers.
If DNA testing would not be helpful, carrier testing can also be done by an enzyme test on a skin sample.
How many people have MCAD?
About one in every 15,000 babies in the United States is born with MCAD.
Does MCAD happen more often in a certain ethnic group?
MCAD happens more often in white people from Northern Europe and the United States. About 1 in every 70 Caucasians is a carrier for MCAD.
Does MCAD go by any other names?
MCAD is also sometimes called:
- ACADM deficiency
- MCADH deficiency
What is the treatment for MCAD?
Your baby's primary doctor will work with a metabolic doctor to care for your child. Your doctor may also suggest that you meet with a dietician familiar with MCAD.
Certain treatments may be advised for some children but not others. When necessary, treatment is usually needed throughout life. The following are treatments often recommended for children with MCAD:
|1.||Avoid going a long time without food
Infants and young children with MCAD need to eat frequently to prevent hypoglycemia or a metabolic crisis. Your metabolic doctor will tell you how often your child needs to be fed. In general, it is often suggested that infants be fed every four to six hours. Some babies need to eat even more frequently than this. It is important that infants be fed during the night. They may need to be woken up to eat if they do not wake up on their own. Your metabolic doctor and dietician will give you an appropriate feeding plan for your infant. Your doctor will also give you a ‘sick day’ plan, tailored to your child's needs, for you to follow during illnesses or other times when your child will not eat.
Your metabolic doctor will continue to advise you on how often your child should eat as he or she gets older. When they are well, many teens and adults with MCAD can go without food for up to 12 hours without problems. Most children do not have metabolic crises past the age of ten. However, some may need to continue treatment throughout life.
Ask your doctor whether or not your child needs to have any changes in his or her diet.
Your doctor will decide whether or not your child needs L-carnitine. Unless you are advised otherwise, use only L-carnitine prescribed by your doctor. Do not use any medications without checking with your doctor.
Call your doctor at the start of any illness
Children with MCAD need to eat extra starchy food and drink more fluids during any illness - even if they may not feel hungry - or they could develop hypoglycemia or a metabolic crisis. Children who are sick often don't want to eat. If they won't or can't eat, they may need to be treated in the hospital to prevent problems.
Ask your metabolic doctor if you should carry a special travel letter with medical instructions for your child's care.
With prompt and careful treatment, children with MCAD usually live healthy lives with typical growth and development. The goal of treatment is to prevent long-term problems. However, children who have repeated metabolic crises may have life-long learning disabilities, spasticity, chronic muscle weakness or other effects.
If MCAD is not treated, what problems occur?
MCAD can cause bouts of illness called metabolic crises. Children with MCAD often show effects for the first time between three months and three years of age. Some of the first symptoms of a metabolic crisis are:
- extreme sleepiness
- behavior changes
- irritable mood
- poor appetite
Some of these other symptoms may also follow:
If a metabolic crisis is not treated, a child with MCAD can develop:
- breathing problems
- coma, sometimes leading to death
Between episodes of metabolic crisis, people with MCAD are usually healthy. However, repeated episodes can cause permanent brain damage. This may result in learning problems, mental retardation or spasticity.
Symptoms often happen after having nothing to eat for more than a few hours. Hypoglycemia can occur, with or without other symptoms of metabolic crisis, just by going too long without food. Hypoglycemia can cause a person to feel weak, shaky, or dizzy, and to have clammy, cold skin. If not treated, hypoglycemia can lead to coma and even death.
Hypoglycemia and metabolic crises are also more likely to occur when a person with MCAD gets sick or has an infection.
Some children with MCAD have very mild symptoms or no symptoms at all.
Where can I find more information?
Minnesota Family Support for Fatty Acid Oxidation Disorder (FAOD) Contact: email@example.com
Medically Prescribed Formula: a table that provides a list of commonly prescribed medical foods and formulas and /or medication for this disorder.
National Library of Medicine Genetics Home Reference: MCAD Deficiency http://ghr.nlm.nih.gov/condition/medium-chain-acyl-coa-dehydrogenase-deficiency
Fatty Oxidation Disorders (FOD) Family Support Group
Organic Acidemia Association
United Mitochondrial Disease Foundation
Children Living with Inherited Metabolic Diseases (CLIMB)
For additional genetics information and resources:
- Genetic Alliance
- Region 4 Genetics Collaborative
- Partnering with your Doctor The Medical Home Approach: A guide for families with children who have genetic conditions - The Guide is intended to be a user-friendly, hands-on tool to support families of children who have genetic conditions to move forward in obtaining and providing a medical home for their children. The guide provides definitions, examples and tools for families to use when working with the doctor to develop a medical home.
More help available from Children and Youth with Special Health Needs (CYSHN):
- Resources: Financial and Other
- Early Childhood Intervention
- Resources for Children and Families
- Youth and Young Adults - Planning for the Future
- Emergency Planning
- Medical Home
We would like to acknowledge the Star G Project. The information on the fact sheet was obtained from the Star G Project. For the most up-to-date information on the disorder please visit their web site at http://www.newbornscreening.info. Each fact sheet was extensively reviewed by family support groups, metabolic specialists across the country and the Star G steering committee.
THIS INFORMATION DOES NOT PROVIDE MEDICAL ADVICE. All content, including text, graphics, images and information are for general informational purposes only. You are encouraged to confer with your doctor or other health care professional with regard to information contained on this information sheet. After reading this information sheet, you are encouraged to review the information carefully with your doctor or other healthcare provider. The Content is not intended to be a substitute for professional medical advice, diagnosis or treatment. NEVER DISREGARD PROFESSIONAL MEDICAL ADVICE, OR DELAY IN SEEKING IT, BECAUSE OF SOMETHING YOU HAVE READ ON THIS INFORMATION SHEET.
|Updated Wednesday, 01-Aug-2012 13:55:00 CDT|