Stridor as the major presenting symptom in riboflavin-responsive multiple acyl-CoA dehydrogenation deficiency

Abstract

Inspiratory stridor of unknown origin was the␣leading clinical symptom in an 11-month-old boy. The stridor increased over a period of 4 weeks, and assisted ventilation became necessary. Selective urinary screening by gas chromatography/mass spectrometry analysis revealed excretion of ethylmalonic and 3-OH-isovaleric acid and of n-isobutyryl-, n-2-methylbutyryl-, n-isovaleryl-, n-hexanoyl- and n-suberylglycine. Neither hypoglycaemia nor metabolic acidosis were noticed. Treatment with 200 mg of riboflavin per day led to a␣dramatic clinical improvement with restoration of normal respiration and an increase in muscular tone within 2 months. During this period, metabolite excretion in urine completely normalized. Riboflavin-sensitive multiple acyl-CoA dehydrogenation deficiency was confirmed in cultured fibroblasts. With riboflavin supplementation, the development of the child has been favourable, with normal school attendance now at an age of 9 years.

Conclusion As respiratory symptoms might precede other symptoms in disorders of mitochondrial oxidation, we propose determination of urinary organic acids in all cases of unexplained laryngeal stridor.