Guidance

Isovaleric acidaemia (IVA): mild IVA

Updated 18 November 2021

Applies to England

Public Health England (PHE) created this information on behalf of the NHS. In this information, the word ‘we’ refers to the NHS service that provides screening.

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This information is for parents if their baby has been diagnosed with IVA 932C>T variant (also known as ‘mild IVA’) following their newborn blood spot screening test (‘heel prick test’). It will help you and your healthcare professionals to talk through the next stages of your baby’s care.

About mild IVA

Isovaleric acidaemia (pronounced iso-val-air-ik acid-ee-mia), or IVA, is a rare but treatable inherited metabolic disorder that prevents the normal breakdown of protein. Babies with IVA inherit two faulty copies of the gene for IVA, one from each parent.

When we eat, our body breaks down protein in food into smaller parts called amino acids. Enzymes, which are chemicals found naturally in our body, then break down the amino acids further so they can be used.

In IVA, an enzyme called isovaleryl-CoA dehydrogenase is missing, which leads to problems breaking down the amino acid leucine. This causes a harmful substance called isovaleric acid to build up in the body.

The 932C>T variant is a mild form of IVA. The risk of problems for babies with this variant is much lower than for those with the more serious variant of the disorder. Babies with mild IVA do not normally develop symptoms or need treatment while well.

Screening and diagnosis of mild IVA

Newborn blood spot (‘heel prick test’)

When your baby was about 5 days old, your midwife took some blood from your baby’s heel for their newborn blood spot screening test (the ‘heel prick test’). The newborn blood spot screening test measures the amount of a substance called C5-acylcarnitine in the blood. A high level of C5-acylcarnitine suggests your baby may have IVA. This is called a screen positive result.

Diagnostic tests

If your baby has a screen positive result, you will be seen by a metabolic doctor, dietitian and nurse specialist (the ‘metabolic team’). The team will provide advice and support. Blood and urine tests will be carried out to confirm if your baby has IVA. These tests will also determine whether your baby has the 932C>T variant.

You will need to wait a few days for the test results to be reported. During this time, you can continue to breastfeed or give normal infant formula. If your baby becomes unwell, you should to take them to hospital for further assessment.

Treatment

If your baby does have mild IVA, the metabolic team will explain the condition in more detail and answer any questions you might have.

No special diet or medical treatment is required unless your baby becomes unwell.

What to do if your baby gets ill

If your baby becomes unwell, they might have an episode known as a metabolic crisis (also known as metabolic decompensation). This is caused by a rapid build-up of isovaleric acid and other related substances in their body, which can make them severely unwell.

Symptoms of a metabolic crisis include:

• irritability
• sleepiness and non-responsiveness
• floppiness and falling over
• poor feeding
• breathing difficulties
• seizures
• coma

A metabolic crisis can lead to serious illness and long-term brain damage, and can be life-threatening.

To help prevent this from happening, you will be taught to give an emergency regimen, which involves specialist feeds and frequent feeding. If your baby becomes very unwell, they might need to be admitted to hospital.

The metabolic team will teach you how to look after your child during illness.

The emergency regimen

The emergency regimen is a glucose polymer feed. It is given regularly, day and night, to provide energy and help limit the build-up of harmful substances in the body.

You should start the emergency regimen if your baby becomes unwell or is not tolerating their usual feeds. Your metabolic dietitian will teach you:

• how to prepare the emergency feed
• how much feed to give your baby
• how often you should feed your baby

Your GP will be asked to prescribe the glucose polymer powder.

The emergency regimen guidelines are available from the British Inherited Metabolic Diseases Group (BIMDG) website.

You should contact the metabolic team at the start of any illness to let them know your baby is unwell and that you have started the emergency regimen.

Signs of illness may include:

• fever
• vomiting
• cough or cold
• sore throat
• chest infection
• diarrhoea
• not being their usual-self

You should take your baby to hospital immediately for further assessment if they do not tolerate the emergency regimen or their symptoms are getting worse.

You should take with you any information you have been given about IVA, including your:

• emergency regimen instructions
• BIMDG guidelines
• glucose polymer powder and scoops

Long-term outlook

With prompt use of the emergency regimen, the outcome is very good and most children with mild IVA will avoid any long-term health problems.

Your other children

At-risk siblings

Children from the same parents have a 1 in 4 chance of having IVA. Your other children might be at risk of IVA even if they have never shown any symptoms. It is therefore very important to get them tested if they have not been previously screened for IVA. Your metabolic team will be able to arrange this testing.

Future children

A new baby from the same parents will also have a 1 in 4 chance of having IVA. When you find out that you are pregnant, you should tell your midwife and GP there is a family history of IVA. You should also inform your metabolic team early in the pregnancy.

The metabolic team will write a birth plan for you. This will include advice on an early screening test for your new baby which should be taken between 24 and 48 hours after birth. This blood test will be in addition to the routine newborn blood spot screening test. The birth plan will be given to you and shared with your obstetrician and local midwifery team.

You should notify your metabolic team once you have given birth so they can ensure the correct blood tests are taken and sent to the screening laboratory without delay.

Confidentiality

The NHS screening programmes use personal information from your NHS records to invite you for screening at the right time. Public Health England also uses your information to ensure you receive high quality care and to improve the screening programmes. Find out more about how your information is used and protected, and your options.

More information and support

The metabolic team will be happy to discuss any queries you might have.

Further information can be found at Metabolic Support UK. The Metabolic Support UK team can be contacted at:

• 0845 241 2173 or 0800 652 3181
• contact@metabolicsupportuk.org

The BIMDG website has the emergency regimen guidelines.

NHS.UK has information about IVA and newborn blood spot screening.