Diagnosis, treatment, and long-term outcomes of late-onset (type III) multiple acyl-CoA dehydrogenase deficiency.

We report 4 children with late-onset (type III) multiple acyl-CoA dehydrogenase deficiency, also known as glutaric aciduria type II, which is an autosomal recessive disorder of fatty acid and amino acid metabolism. The underlying deficiency is in the electron transfer flavoprotein or electron flavoprotein dehydrogenase. Clinical presentations include fatal acute neonatal metabolic encephalopathies with/without organ system anomalies (types I and II) and late-onset acute metabolic crises, myopathy, or neurodevelopmental delays (type III). Two patients were identified in childhood following a metabolic crisis and/or neurodevelopmental delay, and 2 were identified by newborn metabolic screening. Our cases will illustrate the difficulty in making a biochemical diagnosis of late-onset (type III) multiple acyl-CoA dehydrogenase deficiency from plasma acylcarnitines and urine organic acids in both symptomatic and asymptomatic children. However, they emphasize the need for timely diagnosis to urgently implement prophylactic treatment for life-threatening metabolic crises with low protein/fat diets supplemented with riboflavin and carnitine.