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OPINION

Identifying MCADD risk in the antenatal period: tips for healthcare professionals

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The National Genetics Education and Development Centre discuss MCADD, the risk it presents for newborns and recommended treatment guidelines for nurses.

What is MCADD?

MCADD (medium-chain acyl-CoA dehydrogenase deficiency) is an inherited metabolic condition. Around 60 babies in England are diagnosed with the condition each year by newborn screening.

Usually the body utilises fat for energy when there is poor food intake or during periods of clinical stress such as infections, vomiting or diarrhoea.

People with MCADD are unable to break down medium-chain fats due to the lack of functioning MCAD enzyme. Neonates are particularly vulnerable as feeding patterns may not have been established effectively. Babies with MCADD may present with seizures, vomiting, lethargy, hypoglycaemia and their condition can rapidly progress to a coma and sudden death.

This genetic condition follows an autosomal recessive pattern of inheritance which means for children to be affected, both parents must carry an altered gene for the condition but the parents themselves do not have MCADD.

Children with the condition have two copies of the altered gene, one inherited from each parent. It is estimated that around 1 in 80 people is a carrier for MCADD.

New guidance on identifying babies at risk

The National Patient Safety Agency (NPSA) guidelines ‘Keeping newborn babies with a family history of MCADD safe in the first hours and days of life’ state the need for an accurate family history to be taken, documented and acted upon during the antenatal period.

Parents who already have a child with MCADD will usually be aware of their chance of having another baby with this condition (which is a 1 in 4 chance).

However, any history of MCADD in the extended family of either parent should be investigated. It is advisable that in this situation, parents should be referred to a paediatrician or genetics service for advice. This may involve collection of a detailed family history, genetic risk assessment and carrier testing if appropriate.

When asking about a family history, people may not know the exact name of the condition, especially if it is in an extended family member. You may wish to consider the following prompts when asking about a family history:

  • Are there people in the family who feel very ill or faint if they haven’t eaten?
  • Are there people in the family who get seriously ill and have to go to hospital very quickly, even with simple infections?
  • Have there been unexpected deaths, particularly in babies or children, who failed to thrive?
  • Have there been any unexpected deaths, in teenagers or adults, linked to a bout of ‘excessive’ drinking of alcohol?
  • Are there any family members, who are not diabetic, who have been told they have to carry high energy food with them and wear alert jewellery?
  • Are there any children in the family who see a dietitian or health care professional because they need to eat regularly or else they become very tired or may faint?

Implications for nurses

Babies who have been identified as being at risk for MCADD in the antenatal period should have a pathway of care implemented and documented in the mother’s notes as recommended by the UK Newborn Screening Programme Centre. The British Inherited Metabolic Diseases Group (BIMDG) has guidance of the management of newborn babies with a family history of MCADD. They specify the importance of ensuring that the baby has a good milk intake. A term baby, ‘at risk’ from MCADD, should be fed every four hours from birth and a preterm baby every three hours. BIMDG also recommend that breast-fed babies are given routine top-ups of formula milk as it is difficult to know how much breast milk is being taken.

If a baby presents during the neonatal period with seizures, lethargy or coma, family history may help in the differential diagnosis as this information may not have been identified or followed up during the antenatal period. The questions outlined above may prove useful in elucidating this information.

The NHS National Genetics Education and Development Centre has a range of resources on collecting family history information. eLearning resources about MCADD for healthcare professionals are currently in development and will be available free of charge from the website shortly.

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