Glutaric aciduria type 1 (GA1)

Glutaric aciduria type 1 (GA1) is a rare but serious inherited condition.

If you have GA1 your body cannot break down certain amino acids, which are the building blocks your body uses to create proteins. This leads to a build-up of harmful substances in your blood and urine.

Babies with GA1 are not able to break down the following amino acids:

• lysine
• hydroxylysine
• tryptophan

These amino acids are usually broken down into a substance called glutaric acid, which is then converted into energy.

Babies with GA1 do not have the enzyme that breaks down glutaric acid. This leads to a harmfully high level of this and other substances in the body.

Screening for GA1

At around 5 days old, your baby will be offered heel prick screening to check if they have GA1. This involves pricking your baby's heel to collect drops of blood to test.

If your baby has GA1

If GA1 is diagnosed, your baby can have treatment straight away to 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 GA1 are able to live normal, healthy lives. But they need treatment for GA1 for life.

Without treatment, severe and life-threatening symptoms can happen, such as seizures (fits) or falling into a coma.

Someone with untreated GA1 is also at risk of brain damage, which can affect muscle movement. This may lead to problems walking, talking and swallowing.

Symptoms of GA1

Symptoms of GA1 usually do not appear until a few months after birth. But some babies are born with a larger-than-average head (macrocephaly).

Children with GA1 may also have some floppiness or weakness in their muscles (hypotonia) during their first year.

In rare cases, they may have bleeding around:

• their brain (subdural haematoma)
• the back of the eyes (retinal haemorrhage) - very rare

Metabolic crisis

Someone with GA1 may have episodes known as a metabolic crisis. This can happen early on in life.

Symptoms of a metabolic crisis include:

• poor feeding or loss of appetite
• lack of energy
• unusual movements, such as spasms
• vomiting
• irritability
• finding it hard to breathe

It's important to get medical help immediately if your baby develops symptoms of a metabolic crisis. Your metabolic team will tell you how to 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 GA1

GA1 is treated with a specialised low-protein diet and medicine.

Diet

Children diagnosed with GA1 are referred to a specialist metabolic dietitian and given a low-protein diet.

A low-protein diet reduces the amount of lysine and tryptophan. These are the amino acids which your child 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 GA1 may 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

Medicine

Your child will be prescribed a medicine called L-carnitine, which helps to clear some of the excess glutaric acid. They will need to take L-carnitine regularly, as directed by their doctor.

Breastfeeding and GA1

Breastfeeding is possible for babies with GA1. 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.

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 GA1 before.

When in hospital, your baby can be monitored and treated with intravenous fluids (given directly into a vein).

How a child inherits GA1

The gene that causes GA1 is passed on by parents. The parents usually do not have any symptoms of the condition.

A baby needs to receive 2 copies of the affected gene to develop the condition - 1 from their mother and 1 from their father.

If the baby inherits the gene from only 1 parent, they will not have GA1, but they will be 'a carrier'.

If you're a carrier of the affected gene and you have a baby with a partner who is also a carrier, your baby has a:

• 1 in 4 chance of developing GA1
• 1 in 2 chance of being a carrier of GA1
• 1 in 4 chance of receiving a pair of normal genes

It's not possible to prevent GA1. 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 GA1 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