What is maple syrup urine disease (MSUD)?
MSUD is a rare genetic disorder where enzymes in the body can’t break down certain amino acids. Amino acids are the chemicals in the body that help to make proteins – often known as ‘the building blocks of protein’. The amino acids affected by MSUD are leucine, isoleucine and valine.
Amino acids come from foods such as milk, fish and meat and are important for growth and repair. When these chemicals can’t be broken down properly, they build up causing health problems if not treated.
MSUD is inherited when a baby inherits an altered gene from each parent. A parent who is a carrier of the gene will be healthy.
What causes maple syrup urine disease (MSUD)?
MSUD is caused by a change in the body’s genes. There are three genes that work together to make an enzyme responsible for breaking down those amino acids.
If there’s a problem with any one of these genes, the enzyme doesn’t work properly. This means the body can’t process those amino acids as it should, and waste substances start to build up. Over time, these substances can become harmful, especially to the brain and nervous system.
What are the symptoms of maple syrup urine disease (MSUD)?
The symptoms of of MSUD depend on which type your baby or child has:
- Classic MSUD is the most common and severe form. The enzyme responsible works only a little or not at all. Your baby will show symptoms shortly after birth. You may notice them being very sleepy, being sick, or not feeding well. Their nappy will have a sweet smell – which is where MSUD gets its name.
- MSUD occurs in older babies and children. The enzyme works a little better. You notice your child having trouble hitting milestones and not eating well. Usually a special low-protein diet can help control the build-up of amino acids in the body.
- Intermittent MSUD is noticed in older children. Enzymes work well most of the time, but illness and stress can affect how well they work. Your child may become poorly quickly as amino acid levels rise. Getting medical treatment early can avoid any lasting effects.
- Thiamine-responsive MSUD is a much rarer form which can be improved with a high dose of vitamin C. Regular checks can help prevent any future build up.
In all types, MSUD should be treated quickly. If the condition is left it can lead to:
- Seizures
- Breathing difficulties
- Loss of consciousness
Occasionally a liver transplant may be considered as an effective form of treatment, that can help avoid any severe symptoms.
Living with a rare condition can feel overwhelming at first, but it’s important to remember that families are not alone. MSUD is one of several inherited metabolic conditions which share many similarities with conditions such as phenylketonuria (PKU), tyrosinaemia and homocystinuria. Understanding these conditions can help families manage them with confidence and strength.
Our charity hopes to bring together families affected by these conditions, to share experiences and advice, helping you find support in one another.
