MCAD Deficiency – Symptoms and Causes
Overview
Medium-chain acyl-coenzyme A dehydrogenase (MCAD) deficiency is a genetic disorder. It impairs the body’s ability to convert certain fats into energy. This condition affects metabolism—the body’s energy production processes.
Without treatment, people with MCAD deficiency may experience severe fatigue, liver problems, coma, and other serious health complications. Blood sugar levels can drop dangerously low (hypoglycemia). Even when blood sugar appears normal, immediate treatment is necessary.
Metabolic crises can be triggered by:
- Common illnesses
- High fevers
- Digestive problems
- Going too long without eating (prolonged fasting)
MCAD deficiency is a lifelong condition present from birth. Fortunately, all states in the US include MCAD deficiency in newborn screening programs, as do many other countries worldwide.
When diagnosed and treated promptly, people with MCAD deficiency can effectively manage the condition through dietary changes and lifestyle adjustments.
Signs and Symptoms
MCAD deficiency typically shows up in babies and young children. In some rare cases, it’s not found until adulthood.
People with MCAD deficiency may have different symptoms, including:
- Vomiting
- Low energy levels
- Weakness
- Low blood sugar
A metabolic crisis can happen suddenly and may be triggered by:
- Not eating for too long
- Skipping meals
- Common illnesses
- High fever
- Stomach problems with vomiting and diarrhea
- Heavy exercise
When Medical Help Is Needed
Many countries, including the United States, test newborns for MCAD deficiency. After your initial check-up, you might be sent to a doctor who specializes in this condition. You may also work with other healthcare professionals like dietitians.
If you have MCAD deficiency, contact your healthcare team when you have:
- High fever
- Loss of appetite
- Stomach or digestive issues
- An upcoming medical procedure requiring fasting
Early medical attention during these situations is important to prevent serious complications.
Causes
MCAD deficiency occurs when a person lacks sufficient medium-chain acyl-CoA dehydrogenase enzyme in their body. This enzyme deficiency prevents proper breakdown of medium-chain fatty acids, which are important energy sources.
When these fatty acids cannot be converted to energy, two main problems arise:
- Energy Shortage: The body cannot produce enough energy from these fats, leading to low blood sugar (hypoglycemia).
- Toxic Buildup: Fatty acids accumulate in tissues and can damage organs.
The root cause is genetic. MCAD deficiency results from mutations in the ACADM gene, which contains instructions for making the needed enzyme.
This condition follows an autosomal recessive inheritance pattern. This means:
- Both parents must pass a mutated gene to their child
- Parents are typically carriers (have one mutated gene, one normal gene)
- Carriers show no symptoms themselves
- Each child of carrier parents has a 25% chance of developing the condition
People with only one mutated gene remain carriers but do not develop symptoms. However, they can pass this gene mutation to their children.
Risk Factors
MCAD deficiency occurs when a child inherits two copies of the affected gene—one from each parent. Both parents must be carriers of this gene for the child to be at risk.
Carriers have one copy of the gene but don’t typically develop the condition themselves. If both parents are carriers, each child they have faces a risk of inheriting two copies.
Children who receive only one copy of the gene from a parent will not develop MCAD deficiency but will become carriers themselves.
Complications
Untreated metabolic crisis from MCAD deficiency can cause serious health problems. These include seizures, liver damage, brain injury, coma, and death.
These complications can develop quickly when the body cannot properly break down fats for energy.
