Maple syrup urine disease (MSUD) is a rare but serious inherited condition.
It means the body cannot process certain amino acids. Amino acids are the 'building blocks' of protein.
Someone with MSUD is unable to break down the amino acids leucine, isoleucine and valine. This causes a build-up in the blood and urine. Very high levels of these amino acids are harmful.
A symptom of MSUD is sweet-smelling urine. This gives the condition its name.
Screening for MSUD
Babies are screened for MSUD as part of heel prick screening. They are offered heel prick screening when they are 3 to 5 days old.
If your baby has MSUD
If your baby has MSUD, they can get treatment which will reduce the risk of serious complications.
Your baby will be seen in the National Centre for Inherited Metabolic Disorders (NCIMD), Children's Health Ireland at Temple Street. They will be cared for by a specialist metabolic team, including a metabolic doctor, nurse and dietitian.
With early diagnosis and the correct treatment, most people with MSUD are able to live normal, active lives. But they need treatment for MSUD for life.
Without treatment, severe and life-threatening symptoms can happen. These include seizures (fits), falling into a coma or even death.
Someone with untreated MSUD is also at risk of brain damage and developmental delay.
Symptoms of MSUD
Symptoms of MSUD usually appear within the first few days or weeks after birth.
Your baby may have:
- sweet-smelling urine and sweat
- poor feeding or loss of appetite
- weight loss
Metabolic crisis
Someone with MSUD may have episodes known as a metabolic crisis. This can happen early on in life.
Symptoms of a metabolic crisis include:
- lack of energy
- vomiting
- irritability
- breathing difficulties
It's important to get medical help immediately if your baby develops symptoms of a metabolic crisis. Your metabolic doctor will give you advice to help you recognise the signs.
In some cases, a metabolic crisis may be triggered later in childhood by an infection or illness.
The hospital will give you emergency treatment instructions to follow if your child is ill. These can help reduce the risk of a metabolic crisis.
Treating MSUD
MSUD is usually treated with a special diet and supplements.
Diet
Babies diagnosed with MSUD are referred to a specialist metabolic dietitian and given a specialised low-protein diet.
This reduces the amount of leucine, valine and isoleucine. These are the amino acids someone with MSUD cannot break down.
High-protein foods need to be limited.
These include:
- meat
- fish
- cheese
- eggs
- pulses
- nuts
Your dietitian will give you detailed advice, as your baby still needs some of these foods for healthy growth and development.
People with MSUD need to follow a restricted protein diet for the rest of their life. This is to reduce their risk of a metabolic crisis.
As your child gets older, they will need to:
- learn how to control their diet
- stay in contact with a dietitian for advice and monitoring
Supplements
Some people may need to take isoleucine and valine supplements. This helps to keep a healthy level of these amino acids in the blood. They will have blood tests to check these levels.
Breastfeeding and MSUD
Breastfeeding is possible for babies with MSUD. But it has to be controlled. Your dietitian will explain how to do this.
You can feed your baby regular infant formula, but this may need to be restricted. You may be offered a special formula to supplement your baby's needs.
Emergency treatment
If your child has an infection, their risk of a metabolic crisis increases. Contact the metabolic team and follow their emergency treatment plan and advice.
Your team will give you detailed instructions. The aim is to replace milk and food containing protein with specialised drinks. They will tell you if you need to change the medicine dose.
Emergency action required: Go to your nearest emergency department (ED) if your baby:
- cannot keep their emergency feeds down
- has a high temperature that does not go down
- has symptoms that are getting worse
- has symptoms of a metabolic crisis, such as loss of energy, breathing difficulties or extreme irritability
Your metabolic doctor will give you a specialised medical letter to bring with you in case of an emergency. This is in case the doctors have not seen MSUD before.
When in hospital, your baby can be monitored and treated with intravenous fluids (given directly into a vein).
Liver transplant
In some cases, a liver transplant can be used to treat MSUD. This can reduce the risk of metabolic crisis.
A liver transplant has its own risks. The person will have to take medicine to suppress the immune system (immunosuppressant medicine) for the rest of their life. This is to stop their body rejecting the new liver.
It's important to consider all the pros and cons before deciding to have a liver transplant.
How a child inherits MSUD
The gene that causes MSUD is passed on by parents. The parents usually do not have any symptoms of the condition.
If a baby inherits the gene from 1 parent, they will not have MSUD. But they will be 'a carrier'.
If you're a carrier of the affected genes and have a baby with a partner who is also a carrier, your baby has a:
- 1 in 4 chance of developing MSUD
- 1 in 2 chance of being a carrier of MSUD
- 1 in 4 chance of receiving a pair of normal genes
It's not possible to prevent MSUD. But it's important to tell your midwife and doctor if you have a family history of the condition.
If you have more children they can be tested for the condition as soon as possible and get the right treatment.
You may also wish to consider genetic counselling for support, information and advice about genetic conditions. Talk to your metabolic team about this.
More information
You can get more information about MSUD at the National Centre of Inherited Metabolic Disorders.
Patient and family information and support - metabolic.ie
To speak to a metabolic doctor contact CHI at Temple Street.
Phone: (01) 878 4200