Methylmalonic Acidemia

What is Methylmalonic Acidemia ?

Methylmalonic acidemia (METH-EL-MAL-ON-IC ACID-EEM-EEA) is genetic disorder that affects how protein is broken down in the body. It is a metabolic disorder. About 1 in 20 000 babies are born with methylmalonic acidemia each year in Canada.

Amino acids are the building blocks of protein. Normally, the protein we eat is broken down or “metabolized” in our bodies into amino acids and used for growth and tissue repair.

People who are born with methylmalonic acidemia or MMA are unable to properly break down some amino acids in the food they eat. This is because they are missing an enzyme in their cells. Some people with methylmalonic acidemia have a bit of this enzyme and some have none at all. Some with a bit of the enzyme respond to Vitamin B12 therapy. Those with no working enzyme do not.
A more detailed description
Enzymes can best be described as keys that unlock doors in the body.
Think of the food in our system as a person with a big delivery to make. As long as the person has all the keys, the load can be delivered and everyone gets their packages. When enzymes or keys are missing, the packages cannot be delivered and the delivery person is left with a big load, and no one gets the packages they need to do their job.

Food eaten is like the delivery. In methylmalonic acidemia, when the enzyme is missing, protein cannot be fully broken down for use by the body. It is only broken down to the ‘acid’ stage. This creates problems for the person with methylmalonic acidemia. These acids build up in the blood, fluid around the brain and spinal cord, and urine. The name “methylmalonic acidemia” means methylmalonic acid in the blood. The acid is like the delivery person’s packages. It cannot be delivered to the right place and the pile just keeps growing.
When certain acids build up in the blood, they are like poison in the body. The person may not have an appetite, feel confused, not think clearly, sleep more than usual, or vomit. If the extra acid is not removed quickly, the person may have seizures or may go into a coma.
In untreated methylmalonic acidemia, the balance is upset between having enough protein (to meet body needs) and having too much protein (which causes toxic levels of acid in the blood and body tissues). This imbalance is called metabolic acidosis and can cause:
  • stunted growth,
  • severe kidney problems,
  • bone marrow suppression causing low blood counts, easy bleeding and vulnerability to germs such as colds and flu,
  • osteoporosis, or thinning of the bones,
  • swelling around the brain,
  • brain damage,
  • seizures,
  • coma
Some people with methylmalonic acidemia can have all of these complications and be severely affected whereas others may have only a few complications. It all depends on how much of the enzyme is working in their bodies and if their disorder is well-controlled.
How is methylmalonic acidemia treated?
Therapy needs to begin before complications occur because, once they develop, they are irreversible. Examples of this are kidney problems, bone problems and mental retardation from swelling around the brain. Treatment must be started as soon as the disorder is diagnosed.

The treatment of methymalonic acidemia includes:

1. Diet

People who have methylmalonic acidemia and who have no working enzyme (they do not respond to vitamin B12) need to strictly follow a special diet to stay well.

The first part of treatment is reducing protein in the diet. If less protein is taken in, less acid will accumulate.
Examples of foods that must be eliminated from a low-protein diet are:
• milk and dairy products
• meat, fish, chicken
• nuts (including peanut butter)
• beans
• eggs
Protein in the diet is lowered by avoiding protein-rich foods like meat and milk. Examples of low protein foods are fruits, vegetables and starches. These foods provide calories without loading the body with protein.

Calories are a very important part of the diet. The body can use them for fuel without breaking down its own reserves. If the body does not have adequate fuel in the form of calories, it will actually begin to break down muscle to provide energy. Muscle is protein and will increase acid levels in the same way as eating protein will.

The metabolic dietitian works with people with methylmalonic acidemia to ensure that adequate calories and nutrients are being provided while following this special low protein diet. The amount of food and drink the person can safely consume is monitored by the dietitian and often all foods must be carefully measured to control the amount of protein consumed.
It is often necessary for the person to keep a record of what they eat so that the dietitian can make adjustments to the diet if required.

Eating high protein foods increases acid levels. This puts the person at risk of losing consciousness, having seizures and for developing complications such as kidney failure.

It is not unusual for someone on a low-protein diet to have 2 kinds of vegetables and a baked potato for dinner. However, if these foods were all that the person ate, their diet would be lacking in protein, vitamins and minerals. That is where the special medical formula comes in. It provides all the protein and nutrients normally obtained from high-protein food, but without the amino acids that a person with methylmalonic acidemia is not able to break down. Without this formula, people with Methylmalonic acidemia would be at high risk for many nutritional deficiencies. In order to prevent complications, the person must adhere to this diet for life.

2. Medication

Vitamin B12
B12 is a natural substance found in the body that helps metabolize protein safely. However it only helps people who have a little bit of the working enzyme as it helps to make the enzyme work better. Vitamin B12 is taken by mouth in pill form and is available at health food and drug stores.

Flagyl (or metronidazole) helps to decrease the production of acids by bacteria in the intestines. This helps to decrease the overall acid levels in the blood. Flagyl is taken in pill form and is available by prescription only.

Carnitine is prescribed to people with methylmalonic acidemia (MMA). Taking carnitine is important for people with the disorder for two reasons:
- People with MMA don’t have enough carnitine in their bodies
- the low protein diet doesn’t provide carnitine from natural sources
Carnitine also helps rid the body of toxic metabolites that build up in people with MMA. Carnitine is available in liquid or pill form.
The balancing act
The challenge in treating methylmalonic acidemia is to provide enough protein to meet body requirements without overloading the person with protein waste (acid). Visits to the metabolic clinic are needed to consult with the team and make adjustments to food and medication. Regular blood work is necessary to monitor changes in blood levels and other nutritional indicators.

The delicate balance can be upset by strenuous exercise and illness. Both can cause the acid levels to rise. Extra calories are needed at these times to provide the stressed body with fuel.
How do people get methylmalonic acidemia?
Methylmalonic acidemia is an inborn error of metabolism. It is genetic. This means that the person has the disorder from the time they are conceived. At conception, the baby receives two sets of genetic material, one from the mother, and one from the father. This genetic material, called DNA, acts as a recipe for the baby’s development.

DNA includes information about the baby’s eye and hair colour, sex and even whether the baby will be right or left-handed. DNA comes in units called genes. Each pair of genes gives directions to a certain part of the body.

In methylmalonic acidemia, there is a problem with the genes that give information on how the body breaks down protein. The disorder is caused by getting two copies of the faulty gene that gives the wrong instructions. One copy comes from the mother and one comes from the father. If the child inherits only one copy of the gene, they are a carrier for methylmalonic acidemia but are not affected. There is a 1 in 4, or 25% chance that two carriers of the gene will have a baby with methylmalonic acidemia. Boys and girls are equally affected.

With each pregnancy, there is the same 25% chance of having a child with methylmalonic acidemia. In some families, there may be only one child with methylmalonic acidemia, while in other families, multiple children may be affected.
How can friends and family help?
Learn to recognize the signs of trouble. If you know the person well, you will be the first to notice changes in behavior that suggest the acid levels are too high. For example, the person may become irritable, less active and sleep more than usual. Encourage the person to call the clinic.

If your friend or family member show any of the signs or symptoms of high acid levels or metabolic acidosis, take them to the emergency room immediately. The person with the methylmalonic acidemia has a yellow wallet card with emergency room instructions and phone numbers.
Very high levels of acid in the blood may cause problems like:
• confusion
• vomiting
• increased sweating
• laboured breathing
• loss of consciousness
• seizures
Related Organizations
The Adult Metabolic Diseases Clinic
Vancouver General Hospital
Diamond Health Care Centre
4th Floor, 2775 Laurel Street
Vancouver, BC
V5Z 1M9
(604) 875-5965
Organic Acidemia Association
13210 35th Avenue North
Plymouth, MN 55441
Phone: (763) 559-1797
Fax: (763) 694-0017