Pregnancy & Newborn
Screening Developments
Medium Chain Acyl CoA
Dehydrogenase Deficiency
(MCADD)
What is MCADD
• Medium Chain Acyl-CoA Dehydrogenase Deficiency
• Caused by the lack of an enzyme (‘catalyst’) required to
convert stored fat to energy
• Affects 1 in 10,000 babies born in the UK
• In Scotland screening should identify 5 – 10 cases a year
What is MCADD
• Fatty acids are an important energy reserve (fuel) during
periods of poor calorie intake, fasting or during infections
• Patients with MCADD have a deficiency of an enzyme
necessary for the breakdown of medium chain fatty acids
• Medium chain fats accumulate and make toxic substances
which cause serious symptoms.
Why screen for MCADD
• Early identification results in early treatment reducing risk of
acute life threatening episodes
• Early detection of MCADD allows crisis/sudden death to be
avoided
• Adherence to dietary management - normal life can be
expected
Complications of MCADD
• Because fat fuels cannot be used, these patients quickly use
up glucose and may develop hypoglycaemia
• High levels of partially broken down fatty acids and low blood
glucose concentrations causes the patient to become drowsy,
comatosed and eventually stop breathing
• Short term effects: seizures, cardiac arrest, coma, sudden
death
• Long term effects: developmental and behavioural disabilities,
failure to thrive, cerebral palsy and attention deficit disorder
• 1 in 4 infants die at 1st presentation before diagnosis made
Diagnosing MCADD
• Tandem Mass Spectrometry (TMS)
• Acyl carntine (C8) raised
• Diagnosis confirmed by repeat blood test at follow up visit
• DNA test for common mutations (Dundee laboratory)
• Carriers are not intentionally identified
How is MCADD managed?
• Scottish National Screening Laboratory notify Regional Metabolic
Team (RMT) in Glasgow or Edinburgh
• RMT contacts family by telephone to give screening result and
follow up plan
• RMT informs MCADD Designated Team (MDT)*
• Provide MDT and/or GP, HV or midwife with MCADD resource pack
• Arrange face-to-face consultation by member of MCADD
Designated Team and/or GP, HV or midwife as per local protocol
• Arrange follow up visit with MCADD Designated Team within 24
hours or as soon as practically possible
*MDT may be same as the RMT for some NHS Boards
How is MCADD managed?
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Fasting should be avoided
Parents need to know how to manage a ‘metabolic crisis’
Regular ‘safe’ time between feeds/meals
Treat if vomiting/drowsy with glucose polymer feeds
Emergency – IV dextrose
Refer urgently to clinician who understands condition – metabolic
specialist
• On going care shared between RMT and MDT
How is MCADD managed?
MCADD Resource Pack:
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MCADD is suspected leaflet
Contact details for MCADD Designated Team and the Regional Team
A & E information
GP information
Genetic facts about MCADD
• A child that has MCADD has inherited two altered genes, one
from each parent, both of whom are carriers
• It is thought that between 1 in 40 and 1 in 80 healthy people
are carriers and do not have any symptoms
• MCADD gene found on chromosome 1
• Most common mutation,985A>G found in 85-90% of those
with symptoms, but over 25 other variants found
Genetic facts about MCADD
• For each pregnancy where both parents are carriers, there is:
– 25% chance that the child will be born with MCADD
– 50% chance the child will be carrier of the MCADD gene
– 25% chance that the child will not be a carrier nor have the disease
Additional Management of
MCADD
• Babies must complete a full immunisation programme
• Influenza vaccine is recommended annually
• Some children may require a supplement of a vitamin-like
substance called carnitine to prevent carnitine deficiency
• Anaesthetic procedures require an infusion of dextrose
before, during and following procedure
Family Issues
• Families will require genetic counselling
• Older siblings born before newborn screening started will
need to be tested – arranged by metabolic clinician
• Next child: early testing as well as routine testing