Case 944-- Excessively High Acylcarnitine Values in the New Born Screen of Premature Infant

Contributed by Nicholas Barasch MD MS and Steven Dobrowolski PhD


A 39 y/o G2P1 gave birth to a 33 week old premature baby boy at approximately 22:00 hours. Rupture of membranes occurred at 25 hours prior to birth and, per protocol, the mother was given betamethasone to stimulate lung maturation. The birth occurred without incident and APGAR scores were 7 and 9. The mother's group B strep status was unknown so the baby was given ampicillin/gentamicin prophylaxis. At birth, the baby has a weight of 2405 grams (70th percentile), a length of 50 cm (98th percentile) and a head circumference of 30 cm (27th percentile). Since the baby was premature and tachypnic, he was admitted to the NICU.

Figure 1: Events of the first six days of life.

(Figure 1) Due to the baby's respiratory instability, enteral feeding was initially held until the morning of day 2. The baby was given 10% dextrose in water during this time and maintained on respiratory support until day 3. On day 2, enteral feeding was started and a newborn screening sample was obtained. Enteral feedings for the next three days consisted of Similac Special Care formula. On day 5, feeds were advanced to breast milk and Similac Human Milk Fortifier.

Early on day 6, the newborn screen acylcarnitine profile returned as positive for medium chain fatty acids (Table 1). In-house studies not only confirmed these findings but demonstrated an alarmingly high quantity of C6, C8, C10, and C10:1 acylcarnitines which indicated a diagnosis of MCAD deficiency but also indicated improper and potentially harmful nutritional support was being provided that was contraindicated for a newborn with a defect in medium chain fatty acid oxidation (Figure 2). Assessment of urine organic acids showed excretion of hexanoylglycine, which strengthened evidence for a diagnosis of MCAD deficiency, but in addition massive excretion of medium chain dicarboxylic acids (adipate, subarate, sebacate) which provided furthered evidence for an improper dietary regimen. The baby's diet was switched to Similac Advanced (contains less medium chain fatty acids) and breast milk. The acylcarnitine profile was reassessed at 11 and 14 days (Table 1) which demonstrated moderation of pathological acylcarnitine esters to a point indicating proper management of an MCAD deficient patient. The infant was never found to be hypoglycemic during the entire hospital course.

Figure 2: In-house acyl-carnitine profile #1 (day 6)

IS: internal standard

Table 1: Acyl-Carnitine profile of 14 days


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