Following a minor respiratory illness, a seemingly healthy, developmentally normal 15-month-old girl exhibited repeated episodes of severe lethargy and vomiting in the middle of the night. The parents brought the infant to the ER following a seizure. The child was hypoglycemic and was administered 10% dextrose, but remained lethargic. Blood ammonia was high, liver enzymes were slightly elevated, and urine ketones were only barely detectable. A diagnosis of medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is made. Measurement of which of the following would also be expected in this infant given the current diagnosis?

Question

Quizplus · Accepted Answer

In MCAD deficiency, there is impaired fatty acid oxidation, leading to the accumulation of medium-chain dicarboxylic acids in the blood. Deficiency in MCAD is the most common inherited defect in the pathways of mitochondrial fatty acid oxidation. The most common presentation of infants with this disorder is episodic hypoketotic hypoglycemia following periods of fasting. Although the first episode may be fatal, and incorrectly ascribed to sudden infant death syndrome, patients with MCAD deficiency are normal between episodes and are treated by avoidance of fasting and treatment of acute episodes with intravenous glucose. Accumulation of acylcarnitines (dicarboxylic acids), in particular octanoylcarnitine, is diagnostic.

Following a Minor Respiratory Illness, a Seemingly Healthy, Developmentally Normal