Positive Newborn Screen for MCAD -- Now What?

Stephanie L. Austin, MS, MA; Laura A. Stokowski, RN, MS


July 10, 2014

Editorial Collaboration

Medscape &

Management of MCAD Deficiency

Preventive measures (avoidance of fasting, rapid reversal of catabolic stress) have been shown to prevent morbidity and mortality associated with MCAD deficiency[17,18,19]; and in the absence of any specific treatment for the disorder, these measures are the foundation of management. The prognosis for MCAD deficiency is excellent as long as prolonged fasting is avoided and the individual receives prompt treatment of concurrent illness or infection, such as gastroenteritis, respiratory infections, and influenza.[9]

The parents should meet early with a biochemical geneticist who will follow the child at regular intervals and coordinate the dietary management, including advising the parents on how to maintain an adequate caloric intake not only in the short term (eg, waking the baby for feedings if necessary) but also at feeding transitions, such as when the child is weaned from breastfeeding to formula, when solid food is introduced (eg, the need for bedtime snacks), and thereafter. Most children with MCAD will be able to consume a basic healthy diet, with the exception of avoiding coconut products because these contain primarily MCTs. The parents will also receive guidance about the maximum safe fasting time (6 hours for infants aged 0-4 months, ensuring no hypoglycemia[20]) and a gradual prolonging of the period of tolerated fasting as the child ages, based on an assessment of tolerance. The biochemical geneticist will also assist the parents in communication about the child's needs with daycare, preschool, and school personnel.

Carnitine plays an essential role in fatty acid oxidation and is typically supplemented in patients with MCAD deficiency and low plasma carnitine levels. Without carnitine, long-chain fats cannot be transported into the mitochondrial matrix where beta-oxidation takes place. Carnitine also helps with the urinary excretion of accumulating acyl groups by driving the production of the abnormal acylcarnitines, which are exported out of the cell and excreted in the urine. Ultimately, this process helps maintain a pool of free CoA in the mitochondrial matrix and maintains mitochondrial function (including the partial fatty acid oxidation that does take place).

In the newborn with MCAD deficiency, breastfeeding can continue. This question may arise because of evidence showing that initial C8 levels are higher in breastfed infants than in formula-fed infants, believed to be a consequence of more pronounced relative fasting in newborns when breastfeeding is first becoming established.[11,14,20] Once breastfeeding is well established, the frequency of feeding is the important factor. The infant should feed at least every 3-4 hours with an adequate intake of milk. A supply of expressed mother's milk or formula should be on hand to use if the infant refuses to nurse or the mother becomes ill. A lactation consult is advised if any breastfeeding difficulties are suspected.

Regular assessment of the parents' understanding and reinforcement of education about avoidance of fasting and seeking prompt attention for illness throughout early childhood should be undertaken, along with close coordination between the metabolic specialist and primary care provider.[9] As the child enters adolescence, the risks associated with alcohol use must be addressed. Alcohol, especially binge drinking, lowers blood sugar and can result in fasting during a "hangover," both of which can precipitate catabolism. Anticipatory guidance should be provided about the probable need for hospitalization during otherwise routine childhood illnesses or whenever the child is vomiting, unable to take fluids, or shows signs of lethargy. Intravenous glucose must be administered before any medical procedure or surgery requiring fasting.

Close follow-up of growth and monitoring of the parents' adherence to management recommendations are essential. Studies of the natural history of children with MCAD deficiency show a tendency to become overweight in late childhood, although the reason for this has not been established.[21]


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