This inherited genetic disorder prevents the breakdown of certain fats needed for energy, leading to dangerously low blood sugar levels if not treated.
Medium-chain acyl-coenzyme A dehydrogenase (MCAD) deficiency is an inherited disorder that prevents your body from breaking down certain fats and turning them into energy. Your metabolism involves the processes your body uses to produce energy. MCAD deficiency can cause problems with your metabolism.
If left untreated, MCAD deficiency may lead to severe lack of energy and tiredness, liver disease, coma, and other serious health problems. Also, the level of sugar in your blood can drop dangerously low — a condition called hypoglycemia. Prevention and prompt treatment are essential regardless of blood sugar level. If you have MCAD deficiency, a sudden episode, called a metabolic crisis, can be caused by common illnesses, high fever, stomach problems or going too long without eating, known as prolonged fasting.
MCAD deficiency is present from birth and is a lifelong condition. In the United States, all states test for MCAD deficiency at birth as part of newborn screening. Many other countries also provide routine newborn screening for MCAD deficiency. If MCAD deficiency is diagnosed and treated early, the disorder can be well managed through diet and lifestyle.
MCAD deficiency is usually first identified in babies and young children. In rare cases, the disorder is not diagnosed until adulthood.
Symptoms can vary among people with MCAD deficiency. They may include:
A sudden severe episode, called a metabolic crisis, can be due to:
In the United States and many other countries, newborn screening programs test for MCAD deficiency. After your first evaluation, you may be referred to a specialist in evaluating and treating MCAD deficiency. You may also be referred to other health care team members, such as a registered dietitian.
Contact your health care team if you've been diagnosed with MCAD deficiency and have a high fever, no appetite, stomach or digestive symptoms, or a planned medical procedure that requires fasting.
When you don't have enough of the MCAD enzyme in your body, certain fats called medium-chain fatty acids can't be broken down and turned into energy. This leads to low energy and low blood sugar. Also, fatty acids can build up in body tissues and cause damage.
MCAD deficiency is caused by a change in the ACADM gene. The condition is inherited from both parents in an autosomal recessive pattern. This means that both parents are carriers — each has one changed gene and one unchanged gene — but they don't have symptoms of the condition. The child with MCAD deficiency inherits two copies of the changed gene — one from each parent.
If you inherit only one changed gene, you won't develop MCAD deficiency. With one changed gene, you are a carrier and can pass the changed gene to your children. But they wouldn't develop the condition unless they also inherited a changed gene from their other parent.
In an autosomal recessive disorder, two changed genes are inherited, one from each parent. The parents' health is rarely affected because they have only one changed gene. Two carriers have a 25% chance of having an unaffected child with two unaffected genes. They have a 50% chance of having an unaffected child who also is a carrier. They have a 25% chance of having an affected child with two changed genes.
A child is at risk of MCAD deficiency if both parents are carriers of a gene known to cause it. The child then inherits two copies of the gene — one from each parent. Children who inherit only one copy of the affected gene from one parent typically won't develop MCAD deficiency but will be carriers of the gene.
If metabolic crisis caused by MCAD deficiency is left untreated, it can lead to:
MCAD deficiency is diagnosed through newborn screening followed by genetic testing.
A metabolic specialist, and often a registered dietitian, are usually included in your diagnosis and treatment. Lab tests can be done to help identify problems with your metabolism — the processes your body uses to produce energy. Results can help treat or prevent complications.
Newborn screening at birth allows MCAD deficiency to be diagnosed and treated early, before symptoms occur, preventing complications. Once identified, the disorder can be managed through diet and lifestyle.
The main goal of treatment for MCAD deficiency is to prevent problems caused by your metabolism that can lead to low blood sugar. To maintain blood sugar levels and avoid hypoglycemia:
Your health care team may recommend additional treatment options.
Work with your health care team, including a registered dietitian, to develop a treatment plan tailored to your energy needs. This includes planning for extra complex carbohydrates needed during illness, stress or increased activity.
The length of time that is safe for fasting — going without eating — may vary with age and your health care teamꞌs recommendations. For example, during the first 4 months of life, well infants' fasting time may be no longer than two to three hours. Fasting time may be gradually increased up to 12 hours by 1 year of age. Children and adults should not fast for longer than 12 hours.
Recommendations to prevent low blood sugar called hypoglycemia generally include:
Talk with your health care provider about what to do if symptoms of low blood sugar develop so that you have an emergency plan. Strategies may include:
Parent and family understanding of the condition is critical to ongoing care and prevention of low blood sugar episodes and other complications. Prevention tips include:
If you or your child have MCAD deficiency, wear a medical alert bracelet or necklace and carry a medical card. This lets health care providers know of your condition, even in an emergency. Ask your health care provider about information for health professionals that you can carry with you in case emergency care is needed.
Caring for a child or family member with a lifelong disorder such as MCAD deficiency can be challenging. Consider these strategies: